Need some advice on upgrading computer

I am needing some expert help. I am upgrading my computer and need some advice on which cpu to get. For starters on am on a $500 budget (have to buy a new case $100). The mobo I am looking at is an abit kv8 pro K8T800 pro chipset ($105.00)--I would prefer to stick with ABit. The cpu I am looking at getting is the athlon 64 3200 $282. I can either get the newcastle @2.2ghz w/512kb l2 cache or the clawhammer @2.0ghz w/1mb l2 cache. I cant determine which processor would give me the best bang for my buck. I mainly use my comp for gaming. Can any of you experts out there help me out? Thanks

Current specs
athlonxp 2700
1.5 pc2100
ati x800pro
sb audigy 2
abit kd7a mobo