For a 22" LCD and 16x10 native res gaming, you just have to IMO spend the extra few bucks for the 8800GS. The 8600GTS is the best sub $100 card now, but the 8800GS is so much better and just $110 AR, that you are getting alot more for the money and a card capable of better handling that resolution.
Grab the evga 8800GS. You'll need a 6 pin PCI-e connector and about 26amps or higher on the 12v rail(s). The XFX 8800GS states a 500W PSU or greater (without specifying the 12v requirement) but that is assuming a very loaded QX6700 system and probably taking into account for some lousy 500W generics. I've used a couple 8800GS (and own one myself) and the Antec Earthwatts 430W(30 amp 12v) is powering two of those systems just fine. I bet the Earthwatts 380W would be fine too. Anyway, sounds like it wll be easy for you to find a psu to power it. But, Typically ones without 6-pin pci-e connectors are also low on the 12v rail too.