Wow, this is brilliant feedback, thanks everyone~
Hadn't really considered the i5 before, but I guess I should have! Now I've read reviews, this seems to be a veritable bargain. The P55 mobo also seems to have great reviews, thanks for the pointers.
@Chunc: The reason we need a good CPU is that our artwork is a big interactive artificial life simulation, many organisms living within a medium which is a big fluid simulation, the latter being the big CPU hog. I'm hoping to update the code to take better advantage of multi-core. Here's a screen capture, if you're interested: http://artificialnature.mat.ucsb.edu/fluidspace.html
@Skrying: We were thinking of the SG02-F case for portability (we need to carry this thing on long-haul flights), and to fit in the 12" graphics card that we're being loaned.