Yeah, esp. for video editing the GPU is the key...I'm going to have to get me a 2nd monitor sometime too...Ive done some pretty intense AE comps with like 50 layers that for whatever reason I couldn't pre compose. I was looking at around a 2" preview thumbnail of my video if I had to drag keyframes around en masse.

on the subject of having the right GPU etc, check out this DIY tutorial on building a supercharged "hackintosh" I was reading awhile back:

http://nofilmschool.com/2010/10/build-video-editing-hackintosh-thats-faster/

I'm on an Imac right now but if I ever migrate over to a tower, I might consider ponying up the cash and making one of those.