I own a 7900GS and am extremely happy with my decision (taken last April) . I mainly play TF2 and with a little tweaking it's playable @ medium-high settings @ 1440X900 giving 35-40 fps average. Going to wait till the 4870 (or some equivalent) comes down to 10K level.. Till that time it's going to serve me quite well.
PS: Got a bit carried away Best of luck with the search