You get the best OC out of PC3700 and PC3500 RAM, but other then that it isn't nessisary. 2x 1GB in duel channel is the best option for gaming right now, or 2x 512MB in duel channel. You don't want to fill all of your DIMM slots, it will decrease your performance. Patriot or OCZ provide the most stable and some of the best 2x 1GB Duel channel kits right now, and upgrading from DDR333 to DDR400 is a good upgrade.