Hi Chris, just thought I'd give my thoughts about SLI, when I built Kyles PC last year with 2 PNY 8800GT 512mb cards, I started his build with these cards as base, using a SLI mainboard,AMD 5000+ AM2 cpu,4gigs 800mhz OCZ memory, I will say that I was not impressed by it's SLI test score vs single, back when I was assembling it someone mentioned why I went SLI, well, all everyone talked about was "Moores Better Rule", so I thought SLI was the way to go, I wouldn't do it expecting to see "ANYTHING" more than what you are seeing now, at least in these racing sims, fpshooters may be different but there was no where I could recommend it value wise, it made very little difference even in 3Dmark06 scoring to be of real merit, the only possibility is "IF" your board will use both cards at 2.0 config/16x, on Kyles board it runs 1 card at 2.0/16x but runs SLI at 1.0/8x. Check what your board will allow before getting too excited, just an honest opinion, don't waste your time/money.

Kevin.

Thanks guys, I am aware of the technical aspects and potential shortcomings which is why I want to find a cheap used card to play with. If I can't get it done under $80 or so, I'd just buy the newer card.

Yeah!                             
                       
                               

You don't need the exact same card for SLI, I had a set of an XFX and PoV which also had different default clock speed. I did work like it should. For sim racing you won't see much improvement, but in popular fps games you should.

Like already mentioned: better check your motherboard on what it supports, you really want 2 x16 PCI-E lanes and not 2 x8 PCI-E lanes 

Newer games, graphics work and larger monitors along with the desire to tinker is why I want to pursue this. My mobo does 2x16 PCI-E and my PSU was purchased with SLI in mind.

I know that it isn't necessary to get identical cards, but it sure seems to save some headaches most the time.