Yes to the single 8800GT and maybe to the SLI (I don't remember the requirements for SLI with them). Your unit has 408 watts being supplied to the +12v rails. Divide that by 12 and you get a combined 34 amps which is enough for any single card set-up. If I remember the preview correctly, the 8800GT was supposed to be better than the 9600GT by a little bit. I also see no reason why you wouldn't be able to SLI the 9600's.