My sentiments are echoed throughout this thread regarding the GPU.
The GPU's role in modern computing is becoming very central. More and more we see clever programmers (like Mr.Natress) harnessing the power of hardwired gpu functions, to which I believe the role of the Central Processing Unit as we know it will completely change in the not too distant future. Forget clockspeeds.. forget cores. We've seen IBM's cell processor do things on the playstation 3 that would make a conventional CPU look like a pocket calculator. To get a general Idea, PS3's cell produces 16 TRILLION calculations per second, a PC or Mac does a few billion. Now if you could have that inside your editing suite, it would be, well.. sweet.
So.. going off on a tangent, what was my point... Ah..yes..
The future of computing is EXCITING. In a couple of years, be prepared to forget the notion of cores and clock speed.
For now, a good video card would be a very good idea. On most good PC motherboards, you have a Dual-SLI slot, which allows you to bridge two video cards so that they function as a single unit. This also can bring about massive performance gains in my opinion (Someone correct me if this is not the case).