weed, if you would like to have an i7 AND have the option of going SLI as well as crossfire, you may want to check out EVGA's boards, they have high ratings, and many users on these forums like them. Gigabyte has a few 1366 mobos that support SLI and crossfire as well, so I'd just compare their specs and special feature and see which one you could use more. I don't really know if SLI or Crossfire is the better way to go, but I DO know that ATI's latest HD 5700 and 5800 series are more bang for the buck compared to nvidia's GTX series right now. Those cards also have more future capabilities like DX11. Although now that won't give you much over nvidia, once more DX11 programs come out you will start to see a difference.
Power supply, I think I would go with either an Antec TPQ series, a PC Power and Cooling TurboCool 1000 or 1200 ( ask TD about these, he said PCP&C was just shut down by OCZ, but he may have a few left over), Ultra X3 and X4 power supplies are pretty good, and also the Gigabyte Odins and Zalman PSUs.