Just wondering

Running a P4 on an ECS MB with 768 M of DDR2100 (pretty old) and windows xp sp2. I replaced my FX5200 128 MB with a Radeon 9600 256 MB just out of curiosity. How much difference should I notice in games. I only tried it with CS and the FPS wasn't any higher and the overall gameplay basically seemed the same. I'm not a major game tweaker either so that could help overall but in a general sense I thought there should be some noticeable gains. My AGP slot is only capable of 4X. How much of difference in card performance does that cause?
I'm trying to figure out the next video card and MB I wanna get and I was leaning towards ATI cards around $200 maybe more if I'm willing to spend and ABIT MB or others (suggestions?) Thanks in advance!