I don't think we're on the brink to changing from dual to quad cores, because the vast majority to people are not going to notice the difference. No doubt, we will someday all have a quad core chip in every computer, but right now, it's just not going to happen. A dual core CPU is capable of handling everything 90percent of people are going to do with their computers.

In your case, the choice is all yours. I'm willing to bet that there is very little difference (while running most applications) between the 2.53GHz Core Duo, and the 1.6GHz i7 CPUs. I've got two of those 2.53GHz chips in a couple of computers, and they are extremely fast. However, Intel seems to be trying to make the i7 and i5 CPUs the "future", so you might be 'up to date' for longer if you got one of those.