is there a huge difference graphics wise between 256 bit and 128 bit. right now my video card is 256 bit and also is there a difference between nvidia and ati
The GTS 250 is a pretty good card. It will be able to play most games today at pretty high settings.
Edit: One thing about the 250 is that it supports DirectX10, a lot of newer cards are supporting DirectX11 which makes them a little more futureproof because a lot of games will be requiring that down the road.