You are assuming that Mac OS X (and OpenGL) is equivalent to Windows (and Direct X).
This is not true. Games under OS X require significantly more hardware to operate at the same performance level as their Windows counterpart. I've played numerous modern day games (Borderlands 2, Deus Ex: Human Revolution, Bioshock 2, etc) on OS X and Windows. In every single case, the Windows version of the game performed flawlessly whereas the OS X version did not (it was playable, but not entirely enjoyable).
Sorry, but OS X graphics drivers just suck. It doesn't matter if your iMac is so "super duper" and spiffed up internally, because there's nothing you can do about crappy drivers and a horrible proprietary OpenGL stack propagated by Apple that has only recently became semi-useful in 10.7 and 10.8.
So when I say $500, I don't mean 1:1 feature comparison, because that's not required. In many cases, a lesser PC will perform better then a Macintosh simply because it's running Windows and has access to Direct X. And I'm not even going to mention your comment about finding speakers better then that rubbish they build into the iMac. You might as well be comparing laptop speakers to desktop speakers. It isn't hard at all to find anything that sounds better then the iMac, if only because they'd be actual coned speakers pointing at you on the desk.
Op said he loves gaming and wanted to know what to do.
You are going against his statement and trying your best to sell him on the wrong hardware. I love Mac, don't get me wrong. I spend 24/6 under OS X doing all kinds of stuff I can't even imagine doing under Windows. When it comes to gaming, however, it's rare I even bother with the OS X versions anymore. I don't care if the Mac side of things is gaining traction or how many users there are, because that has nothing to do with the performance of the games. Mac users might be satisfied with 25fps. Most gamers are not, and contrary to your belief, these folks are not a minority. They are the reason why Triple-A companies still exist.
TLDR; if you love games, play them natively. Buy a computer that runs Direct X. Enjoy them the way they were meant to be played from the factory.
-SC
I make no such assumption but the humorous thing lies in you assuming I am assuming. ;-)
Once again, you are not making a 1 to 1 comparison whereby someone could run Windows on the Mac hardware and for many titles would need to since there's very often no Mac version to be had. So that argument about playing the titles better in Windows doesn't wash really. Sure, if the performance improvement is a must for you (I'm sorry to tell you but it simply isn't for everyone) then you could reboot and get that. The hardware is what it is. Therefore yeah, you do need equivalent hardware to get equivalent performance.
I understand there are sometimes issues with some games in OS X versus Windows but I do not believe this is true all of the time. I am fairly sure I've read some commentary on this by Edwin from Feral not long ago in support of what I'm saying in fact. Not all Mac games run like ****, sorry. I think you are exaggerating about this stuff quite a bit. For example, believe it or not when you crank up the settings on World of Warcraft the game is actually somewhat demanding and yet I noticed no difference with same settings on same Mac hardware in either Windows or OS X. So the mileage certainly varies by game.
For example, would you tell me it completely sucks to play XCOM: Enemy Unknown or Empire Total War in OS X versus Windows on the same hardware? I understand it is possible that settings may need to be a little lower in OS X but that doesn't make the experience suck for I'd venture to say even most people. You know, a lot of us don't waste time firing up FPS counters and testing performance, etc. We just play games and if they appear to run smoothly and look reasonably decent we are generally pretty happy with them without worrying a lot about the current state of drivers, graphics libraries, etc. But if you do certainly that is perfectly fine. You should enjoy your gaming however you like. All I am trying to say is that not everyone is you nor should everyone be just like you in their view which when it comes to the ACCEPTABLE appearance and performance of games is at least somewhat a subjective thing.
As for the speakers, I was simply including them as another cost. I did not get into quality of them at length beyond saying they needed to be as good. You are right. It is not hard to find speakers as good however, they are yet another cost that needed to be factored in. That was the only reason for mentioning them. Personally, I prefer and use Bose speakers myself. Please don't tell me they suck too. I don't care. I like them.
Yes, the OP did say he loves gaming. I love gaming too. I presume you do as well. You didn't really expect everyone to have the same opinion you do, did you? I know I am not surprised to be having this debate with you.
I am not going against the OP's statement at all. I was simply offering my view which differs from yours. You and I are not coming from the same place. You and I do not have the same demands apparently. I personally am unwilling to spend for, make room for and use a Windows box just to turn up settings a little. You feel this is the only way to fly. Well, fine. We both gave the guy our feedback and he can make up his own mind about which way he wants to go. My issue with you was calling the experience of gaming on a Mac "crap" which really it is not. Your subjective view seems to be that it is. You mentioned 25 fps above as if all Mac games run at that on all Mac hardware. Generalizations like that are simply misleading and untrue.
Buying a Mac is like buying any other computer. You get the spec to do what you need and want to do. You can do a lot better than 25 fps gaming on a Mac generally speaking, depending on the game and the Mac, etc. That figure is outright ridiculous. I'm sure you can point to some example or examples of games running at that fps on certain hardware but so what? So you change the settings OR you upgrade to more suitable hardware. That is no different than what a PC user does too.
If you love to play games - play them, how you want to play them, not how the elite tells you that you need to play them. We do not all need liquid cooled rigs with dual video cards, etc. to enjoy gaming. I can do extremes too.

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Then you're missing out on a heck of a lot.
Why is that if they are satisfied with the offerings available? I respect you may not be. That's cool but why can't he be okay with it?
I mean, for very many adult gamers, there is only so much time for this hobby outside of career, family, other interests, yard work, etc. So then it starts coming down to how many choices do you really need (for some folks at least). You buy one game like XCOM and there is 100 hours of gaming. That could be months for a lot of people. By then Napolean and an expansion to CIV 5 are out or maybe you are playing LoTRO or WoW (there goes your time right there), etc.
No platform offers everything. I understand the Mac platform offers less variety than Windows but for a lot of people it is a matter of so what? Who has the time?
And then there is the possibility for a Mac user to go console for other stuff and bingo, who needs Windows at all then really? No problems with choice of titles anymore then unless you have no life outside of gaming I guess and can actually keep up with that many releases over a year between two platforms.
All I am saying in my long winded way is that no, he isn't missing anything. He's doing just fine. We're all different. It's okay to be different.
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In the hope of not detracting from the current of this conversation and thread, i'll add (on a personal note), that i don't hold onto any fantasy of gaming on OSX. I know, and am happy to game on a bootcamp partition, if it means that i also have OSX on the machine that i'm sinking money into. I love osx, maybe naively for its user-friendly interface and bells and whistles, but after years of toying with windows, for day to day use, osx is where i want to stay.
So with the idea in mind that i have around 4.5k to spend (aussie $), and i get 25% reimbursement on 1 apple computer through work, i'm struggling to decide what to do, as i would find it hard to justify building and spending money on a gaming PC if it didn't run OSX. In my mind, i need 1 computer as my "Work station" and one computer for portability and travel, a 13" 2013 retina hopefully. Thoughts?
I still think you might be happiest with a 27" iMac with the top end GPU option and the MacBook of your choice. I would not so casually dismiss the idea of enjoying what titles you can in OS X either. It really is not a fantasy. Probably the simplest way to test this with zero risk is buy some Steamplay titles you like and try them in both environments and see for yourself rather than listen to other people (myself included) telling you what to like as far as that goes. Also, Feral on their site has a number of demos of OS X titles you could take for a spin. You take a nice looking game like LoTRO for a spin in OS X for free and see what you think of performance and visuals there. Hell it is great on my hardware (2011) so I am sure it would be even nicer on yours. That's just a suggestion but I would caution against just taking the naysayers word that playing games in OS X sucks out of hand. Those are some ways to test for yourself. I think you'll be pleasantly surprised by the amount of times you won't feel rebooting is worth bothering with if the title is available for OS X too on hardware that good.