To me, gaming at anything other than huge resolutions a single 8800GTX or GTS will do it and do it very well. But this is the ultimate upgrade path in that you can add another, as needed later on and likely get a very long lifespan out of your system. There's been very few points in the past 5-6 years where you could set yourself up for something like that and at least be reasonably future proofed on the graphics side.
Panasonic 65" VT60 (calibrated by Jeff Meier), Marantz 6005, Kef Q towers/rears Kef Reference center, Win 7 Pro with XBMC, Harmony Ultimate One
Xbox Live: Arbitrage XXL