OK, I'm a noob when it comes to using SLI in my machine, so I'll ask you blokes.
I've been reading things about using a card as a "PhysX card", but I don't really know the appreciable benefit.
What offers the better performance, and how should I set this up? Should I SLI the two 8800s and drop the GTX? Should I just keep the GTX? Add on one of the 8800s as a PhysX card? I have extra power on my PSU, that's no problem. I don't plan on doing a GPU update until DX12 hits (I know Windows 8 is getting 11.1; I'm waiting for a game-changer), whenever that ends up being. The circumstances were unusual and unforeseen, so I might as well make the best of it.
If it helps, here are my specs:
Asus Rampage II Extreme
Genuine Windows 7 Professional 64-bit (soon to be Windows 8 Professional 64-bit)
Genuine Intel Core i7-920 "Bloomfield" SLBEJ OC @ 2.93GHz
9GB DDR3 SDRAM
1TB 7200RPM HDD
NVidia GTX260 @ 896MB
1920x1080, 1600x900 dual monitor setup
SoundMAX Integrated Digital 7.1 High Definition Audio
Pretty much the only thing I'm certain about is that I can't SLI the GTX260 and 8800 together.
EDIT: Was looking at new cards, when did they stop drawing pretty pictures on top? :(
A dedicated PhysX card consume too much power and is too much of a hassle to worth it.
A 8800GT SLI is a little bit more powerful than a single 260, but again consume too much power and you will get compatibility issues and micro stuttering.
Stick with the 260, and you really should thinking about upgrading it.
Stick with the 260 and seriously thing about upgrading to a current GPU. The GTX560 Ti is like $130 and much better.
Stay with your 260 dude, maybe try sell those cards and get a little cash munay!
@JoMate: I meant the 560 Ti. Sorry. I see those online for about $180 on newegg. It's the 550 Ti that is like $130.
Now AMD have shown their hand for the value segment at 28nm, I think it's safe to say that if you want to spend under $160 and don't want to wait for nVidia (how close are we? are nVidia going to beat AMD with their new GPUs? or is AMD doing these terrible price/performance releases because they know nVidia have nothing to really fight back with any time soon and so they're free to make some money and recover the 28nm R&D costs?) that the old AMD cards are the way to go (nVidia only really had lovely parts once you hit the 560, below that they're doing things like cutting the GPU in half to hit the lower prices and that kills the value for a gaming focussed build - basically there is a big hole in the nVidia lineup that the 68x0 cards fit into and a 6870 can go toe to toe in some games with the 560(s)).
Dirt 3 for free isn't a major bonus now that is a budget priced title, but $150 for an AMD 6870 is a great plan if you can't pay to get a high end card and a 6850 for $130 isn't a terrible deal (but the quality of the 6870 deal means you should probably go for that).