If you are going single core get the 3700+ San Diego Core. Best single core for the money benchmarkwise, beats dual core set ups in some games, too. Cost is like $85 I think.
Get a socket 939, 754 is old tech.
but, if i were to get a beter processor, say dual core, would i notice abig difference because my video card isin't the greatest or would the video card bottleneck the cpu?
oh yeah, and i have 1 gig of ram
You won't notice a big difference in games yet between the dual and single core, because games are not designed to take advantage of dual cores. But soon it will. There are some games out there already for dual core. You'll see a big difference in multitasking though. Go with dual core.
What proccesor do you have now? You can get more performance by upgrading the video card instead, to a 7 series card like a 7300gt or higher. I also recommend the 3700 san diego, its the same core as the fx. That along with a 7300gt or 7600gs will play games pretty **** good, on med-hi settings.