CS, and any game based out of the HL engine for that matter, is more CPU intensive than graphics card intensive. If this is the only game you play, you can probably get by with even a V2 running the WickedGL so long as your processor is adequate.
Personally, I'd look into the quality of your RAM (is it PC100 or PC66?) and overclock the CPU to 450mhz. Most of the C300a's produced, especially the retail version, could easily run at that speed, even at default voltages.
Bottomline, don't expect any significant performance boost by upgrading your video card at this time. The C300a is just plain too slow and is a severe bottleneck.