It's 8 months later, and now I'm in the market for the same thing. I've moved onto a sailboat so my big tower really does have to go. I'm figuring it should have an Intel i7 CPU, but what else is really critical?
ALSO: one thing I absolutely want to be able to do is plug in a monitor, and have the two function independently. (That is, drag windows from one to the other and have them run at two different resolutions.) Even though it's a boat, I still get to have a flatscreen bolted to the table and it's great to have SL on one and do actual work on the other. Someone told me that as long as a laptop has an HDMI output, it will do this, but I've never had that confirmed.
Any new laptops out there that I should be looking at? I could go up to $1500 if I have to; I'll have this machine a long time.