Re: Take the plunge and get 6600GT?
For me the 6600gt was a very good a upgrade from a 9600xt (which is similar to 5700U performance). It runs Source, D3 and Q4 at good frame-rates.
So I think if 1024x768 is enough then a 6600gt will do nicely.
[Asus M3A78][Athlon X2 7750 BE][HD3870 512MB][2GB DDR2 800][X-Fi Xtreme Gamer]