Two questions actually.
1. If I were to buy a Mac Pro with the default graphics card, could I replace it with an nVidia 8800, and actually have it work and all?

2. I see there are options for having multiple graphics cards, do these use SLI to work together? Meaning could I theoretically get 2 8800's and run them wilh SLI?

I know the Mac Pro doesn't support SLI. I suspect you would have to flash the 8800 before it would work too.

In order to flash the card, you need a Mac version of the card to dump the flash from.  Right now, its a no go, but the 1900xt is a great card.  Im guessing the next revision of the MP will has the 8800 gts.

yeah it's just that i want to be able to use directx 10 in boot camp, and i can't do that with any of the current card options. I'll probably just wait for them to get dx10 cards then get one. thanks!

The 1900XT is an awesome card... but, I'm going to have to disagree with Maestro here. I do not believe a card like the 8800 GTS/Ultra will EVER be on the Mac Pro. The 88xx series was designed SPECIFICALLY for games. Cards like the 1900 (or the 8600 even), while having gaming in mind, are also viable for graphic design and other pro-sumer work; exactly what the Mac Pro is pitched for. I doubt Steve Jobs and et. al. even considered gaming in their planning.  Just my theory--but it would explian why older, but viable gaming cards such as the Radeon 7950 are still not available (to the best of my knowledge.)

As for DX10 cards, your wait may be over a year. First, most games currently in early development are lacking native DX10 support. OEMs and developers are not ready to justify the cost for such a niche group of Vista gamers. Even the 8800, while supporting DX10, does not see much of an improvement over DX9. Second, the install base for XP is much much larger than Vista--and will be for some time to come. Vista adoption is much slower than XP's and even gamers are hesitant to upgrade because of incompatibility with earlier, popular titles. Not to mention the OS slows virtually all current hardware vs. XP.

This is all just opinion, but as somebody in Dell Management (blasphemy!) I can tell you those are the trends we're seeing. Nobody wanted Vista, especially gamers. This is why the company (Dell) re-released the XP install option.

i understand that to use dx10 i'd actually have to use vista, which sucks, but i'd just like to be prepared for the future

i don't need it to be the 8800, but at least the 8600. Really, i just want a new card.

Just a note of interest, from what I've recently read there has been a game that supposedly that could only run using Vista and with direct X 10, that has been cracked to run under Windows XP and direct X 9.0... So therefore one may just have to wait for people to crack the games to run under the older version and OS.  This probably will happen quite a bit much to MS' sadness because they are using this only for Vista deal to push sales of Vista when most PC gamers are against doing so.  and as far as the 8800 coming to a Mac Pro, I be.live it is quite likely because many of the big game developers are looking towards developing for Mac.  E.A. and ID for example, these and other companies will also take note that also people will be able to run Windows games on their Mac's via Boot Camp, and also there are coming soon solutions to run Windows XP/Vista along side OS X Leopard that are coming from what I've heard.  Is looking forward to the day when a Mac will run Windows based apps without running windows however, like running it through a Rosetta type program or something... 

I don't see why you couldn't run windows apps on mac with Wine from Linux.

8800 cards will not work and will continue down that road until apple releases a version of their own.  Remember apple writes their own drivers for their cards!

if you put an 8800 in a mac and ran windows or linux on it would the graphics work? Or does the ROM apple makes for the card make it compatible with the computer as well as the software?