8800 gt 512mb in SLI??

I have 2 Zotac 512mb 8800 GT's in SLI, and the performance is admirable at 1680 x 1050, but not mind-blowing. I wasn't getting anywhere near 30 fps on Very High on Crysis, although High performed more or less ok. That is, until you get out of the alien ship. After that my frame rate became ridiculously low. I had to turn most of my settings down to medium. CoD 4, on the other hand, is amazing. Easily runs all graphics on high and AAx4 at 60-100 FPS at 1680 x 1050. At this point in time you're probably not going to get a huge performace boost with any other cards besides a 280 GTX or 4870 X2. Or maybe 260s in SLI.

Yeah. It also could have been becuase I was running it in DX10 mode, which makes your framerate go down a lot, although I didn't know it then.

I've got an E6850 30 ghz., but it's currently overclocked to 3.4. My last 3DMark Vantage test gave me a score of H6417, and I'm running Vista 64 with 4 gigs of ram. Now that I look at it, I'm running Warhead in DX9 mode with all settings set to Gamer, no AA, and I'm getting 35-45 FPS.

I would say, if you can afford it, and you don't want to spend the money on a higher end card, SLI is a good choice, and you'll definitely see at least some improvement in your graphics.