Help over clocking my A64 3200+..

[Poopshoot]

Hi everyone im new 2 the forum so i hope i dont sound like 2 much like a retard. Well my Question is...Should i get 512mb of CAS2 PC3200 (XMS, Hyper X..) or one Gig of PC3500 CAS2.5 (kingmax). All i want is better gameplay for COD, FarCry with my G4 MX440. All i need is 200 more dollars till i can order a Radeon 9800Pro.

Specs_____
MSI K8T800 Neo-FISR
Athlon64 3200+ =CLAWHAMMER
256mb Kingmax PC3500, 512mb KingstonValue- I HATE THIS RAM