Can you tell us what your budget is?
512MB cards with a 128-bit bus are much faster, especially with GDDR3-5.
Here are great cards for budget;
*Please note; I do not recommend him the 4870/90 because he wants to play future games.
My budget is about $60 so the HD4670 seems like a good choice for me. Is there any significant difference between a 512MB 128 bit card and a 512MB 256 bit card besides price?