The video card forum is a good place to post.
The general thought there is Gainward BLISS 7800GS if your in the UK.
The eVGA or BFG 7800GS are the US choice
Some will tell you to get a 6600GT.
What CPU are you running and how much RAM?
I upgraded from a 9800 AIW 128 to a BFG 7800GS and it doubled my '03 marks. I used 03 because my mobo and CPU are '03 standards.
I still had studdering issues with BF2 and some other games with 1 GB of RAM. I upgraded to 2 GB and the studdering is gone.
Note: Some will tell you that if you should upgrade to PCIE and get a 7800GT for about $50 more.