What CPU would you choose?
I was considering this one...
Intel Core i7-3930K Sandy Bridge-E 3.2GHz (3.8GHz Turbo) LGA 2011 130W Six-Core Desktop Processor BX80619i73930K
It's like $560 but has great reviews.
I'm definitely getting an SSD and a large HDD. So, I'm already looking at 1.5K all of that. That's not including the video card, case, cooling, disk drive, etc.
That would probably do, though the latest generation of the I7 I have in my dell is a 3.4ghz/3.9ghz turbo boost. I suspect that one would do fine. Don't overlook AMD chips, they have some fast ones as well.
Make sure the motherboard supports a fast bus speed and has the pci express slots (I believe that is what they call it) so you can put a kick ass video card on there (and for all I know, they may have dedicated graphics slots now), you want a video board with as much memory as possible.