Ok, so I've had a 2009 MP (flashed 5,1) for about a year now. Bought it with 2x E5520s at 2.26ghz, 24gb ram, and a HD 5770. I had been going back and forth over getting a non-EFI card for it or not, as so many do, but finally decided to do it. This was being used solely as a work station for video and photo editing, which brings me to my next point. I also have a new ASUS GL502VM ROG gaming laptop. The specs are as follows: i7 7700hq 3.5ghz-ish, 12gb ram, gtx 1060 3gb running windows 10. I absolutely LOVE this laptop! It has handled everything I've thrown at it on ultra, keeping an average of 60+ fps. Games I run regularly: Overwatch (Epic), Starcraft 1 &2, HOTS, Destiny 2 BETA, Crysis 3, Battlefield 4, SW Battlefront, Mass Effect trilogy (mainly 3 multiplayer), and maybe some more that I'm not thinking of. I can play all of these games maxed out, with no issues. Sometimes Crysis 3 will dip into the high 40s on Ultra and full MSAA if there's a lot of particles in frame, but generally stays in the 60s and 70s. Back to the lowly Mac Pro. I went for a PNY GTX 1060 3gb OC XLR8, since I have a solid baseline for it. I was also worried about diminishing returns by going for too high of a card on an old machine. I also never saw VRAM use above 2700 on the aforementioned titles. So, what are the results? Nothing short of AMAZING! This old MP is running with the slow processors, slow ram, and a decent mid-range graphics card. As far as benchmarks go, it beats the ASUS laptop in Unigine Heaven: Ultra, tessellation Normal by about 200 points, Firestrike by about 200-300, and 3d mark Time Spy by over 500 points! The actual gaming holds up just as well. I will get some benchmark screen shots up for proof. So to anyone out there wondering if it's worth it, imo YES it is! Again, I'm not sure about diminishing returns on bigger cards, since I don't have them to test. So use your best judgement. As far as my experience, absolute success and couldn't be happier. Should be interesting to see what higher clock CPUs and RAM gets me. The official CUDA support with Apple (Pascal cards) should also help with editing work. Hope this helps someone, as this is the kind of thing that I was looking for while researching.