Speaking for "The Netkas Group" I can say that GTX580 can be made to work but Hatter is right in that power issue is not easily gotten around.
Best to add an external Power Supply to use GTX480 or GTX580.
There is no EFI for 5xx Nvidia cards so they are ATY_Init only. GTX570 can be easily powered with existing outputs but needs ATY_Init to work. (can be used without helper in 10.7.2 Beta)
There are EFI ROMs for GTX470 and GTX480.
They work perfectly but the need for external juice on 480 is a real downer.
Basically, unless you use software that can get use from CUDA, the ATI cards are better deal. The 6870 can run 4 separate displays at once, the vaunted 480/580 cards just 2. The official Apple 5770 is a sweet spot in terms of value and ease of use.
The Nvidia Fermi cards are for Power users with specific needs.
For editing Gramma's 85th b-day video and watching all the latest You-Tube / Facebook / Twitter dreck, the 5770 is more than sufficient.
EDIT: I am adding the following info that I posted in another thread.
It sums up what cards are OFFICIALLY supported in which Macs. Do what you will with it.
I will make it simple, here is a list of ALL Mac Pro video cards as released by Apple or their partners. These were cards that were either available on the machines, or through retail. Note that there are flashed versions of these cards which can cross borders, but these are the OFFICIAL released cards.
Work in ALL Mac Pros:
ATI X1300
ATI X1900XT
ATI 2600 XT
ATI 3870
ATI 4870
ATI 5770
ATI 5870
Work in 1,1 and 2,1 Mac Pro ONLY (EFI32)
Nvidia 7300GT
NVidia 8800GT (EFI32 version)
Quadro 4500
Work in 3,1 or later Mac Pro (64 bit EFI)
Nvidia 8800GT (EFI64 version)
Nvidia GT120 (aka 9500GT)
Nvidia GTX285
Nvidia Quadro 5600
Nvidia Quadro 4000
You will note that ALL of the ATI cards work on ALL of the Mac Pros (due to EBC EFI)
You will note that Nvidia cards are either/or. The ONLY Nvidia card that is available on BOTH types used a completely different EFI on each version. Thus, an 8800GT that works GREAT in my 1,1 Quad 3.0 will boot to a black screen in my 4,1 Octo 2.26.
Such a simple rule...
ALL ATI CARDS WORK IN ALL MAC PROS
ALL NVIDIA CARDS WORK IN ONE OR THE OTHER.
To add to the confusion, there is no single way that these Macs are referenced. Apple calls the 3,1 Macs the "Early 2008" Mac Pros. So someone who remembers that they bought theirs in February of 2008 thinks theirs is 3,1 and therefore EFI64. What they don't remember is that they got a KILLER deal because OWC was clearing their stock of 2007s and they got a 2,1. They order an 8800GT for a "Early 2008" and get a BLACK SCREEN.
When buying an Nvidia card, whether from an online retailer or EBay auction or garage sale, it is vitally important to know which Mac Pro you have and which Mac Pro the card is designed to work in.
Message was edited by: DPArt