when compiling, the amount of ram doesnt make much difference when your over 1 gig. The speed of the ram will as the processor pulls from ram and pushes back. This is all part of the Front Side Bus issue on processors (whatever intel's i7 chips call it, its still the same thing). The maps we are running are fairly small considering a huge map is around 50 meg.
Compiling doesnt use the graphics card (unless they changed something I dont know about, even then it would be limited to ).
Processor speed and number is going to be your biggest bonus out of your hardware. I still compile on a AMD 2500+ running win2k and will compile any well constructed map i have come up with in under 4 hours for a ldr/hdr final compile. I have determined if VVIS is taking longer than 15 min I did something really wrong (and i dont bother with portals or other visual entities to optimize vvis processing).
if it just running like well...ass...for no reason, start looking at other processes that are running thats using all your processing power. Playing music, watching movies, screensavers, internet downloads, anything else..., will slow your compile dramatically. Set it to compile and walk away.
So, look at your compile times per section (vvis, vrad) and figure out which is taking too long. If its the lights, you cant do much but get a faster processor. If its the vvis, take a look at your map and read up on what VVIS does and how to make it work less.