Amd have a quad core too at the same price - the Phenom 2.6ghz. I've heard they're quite power hungry (more than the intel?). The intel is only 2.4ghz but both clock easily to 3ghz without extra power. Is the intel the better choice though?
I tend to think there is never a good time to buy upgrades. Whenever you decide to buy there will always be new models and price cuts soon afterwards. You just have to decide when you are going to take the plunge and accept that whatever you buy will no longer seem such a good buy next week.