Good question; I have some leeway here, probably $3-4k for the hardware. I noticed the new Mac Pros are pretty beefy and pricey. But I would like to do a fair amount of HD experimentation (playing around!) with products like Final Cut.
If your going to spend that kind of money you should wait for NAB, good chance that apple will announce an 8 core macpro. Current pricing of the quad core chips leads me to believe that the 8 core macpro will not be substantially more expensive than the current quad cores.