Well, dual core isn't really being taken advantage of right now. So his games won't be as fast. However, once games start to utilize dul-cores, you'll be blazin' fast!
The best quotes I've ever heard:
RaistlinZ - "I think God woke up one day (probably around Noon. dude likes to sleep in) and said to himself, "OMFG, these dinosaurs are just kicking too much ass. The world is not ready for them yet." "
The Athelon 64 processor us good all together. However, if you want a really good next generation processor, get a dual-core, you definetly won't regret, and save yourself money from not having to upgrade later on in the future.