Now, you say that the card isn't quite cutting it, and that you get 30-50 fps in CS:S.... What is happening that 'isnt cutting it'? Is it just that you want more fps, or are you seeing slow-downs, and artifacts?
EDIT: What are all of your system specs?
Your price range would put you at an x1650 or 6800/7600 at the top end...
Newegg.com - AGP Video Cards/EDIT