Is a quad absolutely necessary?
If you're not doing much more than that, there's no need for a quad. The quad is only good for extreme multitasking and games that utilize it. A faster-clocked, cheaper dual-core makes more sense to me, one of the new
45nm ones. Testing has shown that they've gone up to (some beyond) 4GHz on
air.
IMO, I think you could get away with a lower-end dual-core. But if you have the money and want to help futureproof your computer, then I guess that's a good reason to go quad.