I have an upgraded 5,1 from 2011. It has 12 cores running at 3Ghz with 48GB of RAM. It has a flashed Gigabyte Radeon 7970 with 3GB of RAM running overclocked, fans are quiet. I have 18TB of spinning drives in the main bays for which eSATA 2 is not an issue. An additional 4 SSDs with 3TB are sitting in an internal bracket driven by CalDigit FASTA-6GU3 cards that also supply USB 3. The WiFi/BTLE card is upgraded to support Continuity.
This is likely as far as this system will go. But it will likely be enough for me for several years.
I would not buy the current Mac Pro configuration. It would only be a marginal improvement and is much harder to customize, which makes it less future proof. I mainly use Mac (although Windows 10 and 7 are on this system in multiple Boot Camps also accessible via VMWare..)
No question, there are cheaper Windows workstation configurations that are more current. But I use macOS and do not want to mess with hackintosh except for fun. My system runs 24/7. There are plenty of other systems in the house. I have a mini as a server and a MacBook Pro Retina (high end made to order) plus 11" Air. The Pro is docked to a Thunderbolt monitor with accessories.
But nothing compares to the quiet, effortless performance of my cPro running one or more VMs with large compiles, video compression, etc., while keeping the tunes humming and mail going.
The "need" for more performance at this time is mainly theoretical and I am not in the market for $1K video cards, even if they could run in this box.
So - it's all pretty individual. I have put a lot into this system, but certainly got my money's worth. And my 2,1 and 3,1 are also still in use also running ElCap.
My hackintosh is a quad core i7-6700K@4.7GHz with 64GB or RAM. I run a reference GTX 980 with 6GB RAM and don't have to worry about EFI firmware for boot screens. The fans in my system are inaudible to me even under full CPU load. I have three 3.5" drives and two 2.5" SSDs all on hot swap bays (which Mac Pros don't have) running off of SATA 3 and an M.2 SSD. USB 3 (as well as 3.1) are built-in to the motherboard. Like you, I used a Wifi/Bluetooth card pulled from more current iMacs for Continuity.
I spent about $1400-1500 to put together my system. I bought the best fans and heatsink I could find which is why the system is inaudible to me even under full load. The fans alone cost me over $80 and the heatsink cost another $60. I wasn't looking to save money on this build. I was looking for a system with the features I wanted. This thing also runs 24/7. That's how I used to have my Mac Pro 5,1 which this system replaced and that's how I will run this.
I also have a Mac mini that runs 24/7 acting as a server and a MacBook. I also have an 8 drive NAS that runs 24/7. Transfers to and from the NAS are extremely fast due to the use of 10GbE.
I also put in a lot in to my old Mac Pro 5,1 before replacing it with my current hackintosh. CPU upgrades to 12 core 3.33GHz. High end video cards. 64GB RAM. PCI-e SSD. SATA 3 card. USB 3 card. 10GbE card. Wifi/Bluetooth upgrade. But nothing could upgrade its inefficiencies. Power consumption was ridiculous and the amount of heat put out by that computer heated up the room enough that it was necessary to crank up the A/C.
Power consumption of my hackintosh vs my old Mac Pro 5,1 3.33GHz 12 core:
Sleep: 5.1W vs 10.1W
Idle: ~80W vs ~170W
Internet surfing: ~90-130W vs ~210W
Full load: ~190-193W vs ~410W
Based on the amount of power a Mac Pro consumes and the amount of heat it puts out, I hardly call the way it performs "effortless". Although normally quiet, once it is put under full load, the fans in my Mac Pro became quite noisy. Again, I don't consider this "effortless". VMs, video compression, iTunes, mail. My hackintosh truly handles this much more "effortlessly" than the old Mac Pro.
Both of us put a good amount in to our 5,1s. I also got my money's worth from that old 5,1. The difference is that you continue to pay for that Mac Pro in the form of increased electric bill and higher air conditioning costs. I've moved on to something that consumes far less power and runs much, much cooler.
I used to have a Mac Pro 1,1 and a 3,1 too. But there's no way I would continue to use either of them today. When I got my Kill-A-Watt, it really changed my thinking on the importance of efficiency.
I loved my Mac Pro 5,1. I will always remember it fondly and it will always be one of my favorite Macs of all time. But it's past its prime. When using high end video cards, the CPU(s) and, to a lesser degree, the PCI-e 2.0 are bottlenecks.
There seems to be misconception here that a hackintosh requires constant tinkering with and is unreliable and can't run 24/7. This just isn't true. Once set up properly, they don't require any more maintenance than any other Mac. There are even a lot of people who have already upgraded to macOS Sierra with little to no tinkering required.
[doublepost=1471334226][/doublepost]
You are much better off buying the 2012 machines. Apple has a policy of keeping a model running for 7 years after introduction, so the 2012 MDXXXLL/A will last until 2019. That means the software will work, and you can bring it in to an Apple store for repairs if all else fails.
The 2008 MacBook lost OS X upgrade support after just 4 years. No amount of hacking could get Mountain Lion to run properly on those systems because Apple never made 64-bit versions of the graphics driver.
I recommend the quad core MD770LL/A. It should cost about $700. Beware many sellers change the firmware on the 2010 models to make them appear to be 2012 machines.
I was unaware of a way to change a 2010 Mac Pro 5,1 to a 2012 Mac Pro 5,1. Please provide a link to the procedure.