Not sure, but if a Sempron 2800+ is the equivalent of a Celeron 2.8GHz, then I'd say that you would get a very decent playable framerate. It'd probably be over 50fps in ET. Not sure about Diablo, don't have it.
i got sempron 3100+ oced but got nforce 3 mobo and a 6600GT and i get 97FPS on AA8x and AN8x... so ull get good enough graphics... but if not then go for 7800GS
hey im planning to get a 6600GT card too, you guys tthink its good? will it do good on games like guildwars..BF2... and doom 3 on 1280x1024 with a athlon 3000+ and 2 gig of ram. (medium settings to high? no aa or af)
doom 3 - will be fine on high settings
guildwars - will be fine also
bf2 - should be able to run on med-high (unsure)
i have a 6600GT AGP and i dont see anything wrong with this card...its great...i plays most games out today.....i will only be upgrading when the G80 comes out