Worth pointing out there that you need a Core i7 if you want to use SLI/Crossfire with both cards running with 16x PCI-E channels. Unlike AMD systems, with Intel it's the CPU, not the chipset, that determines how many PCI-E lanes you have to play with.
On a Core i5, SLI/Crossfire will drop to 8x/8x and forget about 3-way. The performance loss of 8 lanes instead of 16 is not huge, 3-5% framerate loss typically (THG did an article on it a year or two back, you could search it), but personally I'd want every last FPS that my card is capable of!
Also, if you want to run your DDR3 in triple channel (giving a maximum bandwidth of 25.6gb/s), you'll need Core i7. These are the reasons I got my i7 920 (D0), and I haven't regretted it :-)