Depends on your dream
The ultimate dream gaming Mac would depend on your dreams.
Personally, my dream gaming mac would be a modification of the iMac.
Try to follow me on this, I'd love people's feedback.
Take the current iMac design. Move a PCI-E 16 lane to the middle back of the panel. Apple would modify the connection from a dual-sided slot to something smaller, perhaps a BGA or an old style square edge connector.
The new iMac would connect a dedicated video board to the motherboard at this point.. back of the machine.
The base configuration would essentially be internal to the case. There might be a small 'blister' on the back if need be.
The high performance [Gaming] system would use a modern graphics sub-system. To accommodate something like an 9600GT or and 8800GT, the 'module' would likely be large enough to that it would noticeable. I suspect it wouldn't be difficult to engineer and have it look presentable though.
I envision a 'lump' that matched the back. It would be smooth with a flattened 'top' (aka back). The top would be vented.. perhaps laser cut into the back, the whole module skin could be Alu and part of the heat sink. The bottom would also be vented to aid in heat convection. I suspect it wouldn't be difficult to also flow some of the existing internal air flow over the module either.
edit: I had an thought.. envision this: take a thick slice of bread [typical loaf dimensions]. lay it on a counter top.. it would be 1/2, perhaps 3/4" tall at this point and maybe 4-5" square. Now imagine you took some peanut butter butter and smeared it along the edges.. not on the top, but like caulk making a smooth transition from the top of the crust to the counter. This is basically what I think a graphics module would look like in dimension. The bulk of the module would be copper heat sink fins and aluminum skin. one side (top) of the peanut butter edge would have vents cut, the opposite peanut butter edge (bottom) would have vents cut, hopefully for some convection cooling though I suspect you'd need to flow some internal air-flow into it also. Sorry, I couldn't think of a better way to visualize it.
Here's the best part, The module is plugable [retaining screw on each corner] so it would be possible to upgrade. In fact, there's nothing to stop an aftermarket vendor from making a bad ass 9800GX2 module with a big heat sink and fan.
I think it's the perfect gaming rig because the iMac is already a great computer but its major flaw is the lack of truely fast graphics. It would be the ultimate LAN Party Mac and probably the ultimate LAN Party Windows box. 20" or 24" in one panel. It's the quiet home computer (without the ugly box) and it's still a perfectly capable gaming rig for the kids (or the adults).
Well, that's just me.
In general if I were at Apple I'd also pitch the sub-Tower like everyone else mentioned.
1/2 height of current cheeze grater. Same design to take advantage of superior air flow.
800W power
Two SATA bays behind Optical
Ports, Ports, Ports: 6-8 USB2, 2 FW800, 2 E-SATA
Gig-E, built in audio w/ optical out
2x 16 lane PCI-E with SLI support. I don't suspect other PCI-E would be useful.
4 DDR2 slots. At least 8GB RAM support (because, why not?)
Optionally.. a Physix chip would be a selling point if Apple could get good economies of scale.
Given a future release, I would suggest lower mid video so the machine isn't priced out of other market segments but Gaming cards would start at the 8800GT or 9600GT (performance is similar but I believe the 8800 might run cooler). High-Mid and High End ATI and Nvidia cards would be available from Apple (not all, but one from each performance level). Videocard selection would likely be tied to SLI support.
CPU support would be Wolfdale (which are actually pretty inexpensive at 3GHz) and Quad Core from 2.5GHz all the way up to 3.2GHz. Single socket should be plenty
That's it. Personally, I think the super-IMac would be much more interesting.
ffakr
P.S. Apple can take any idea I present in a public forum, I release any claims on my concepts.
At most, they could throw me a solid and offer a job but I wouldn't demand one.
