I7 860 vs. i7 920

I'd say get the i7 920 and OC it.

They both OC to around 4.0GHz on good air cooling, and the i7 920 will perform better if it is at the same speeds as the i7 860. (whereas the i7 860 performs better at stock)

The 1366 mobo will cost $100 more though.

P6T, UD4P, UD3R, UD5P, P6T Deluxe v2, DX58SO, and MSI Gold/Plat are all pretty good 1366 mobos
 
you might want to think of going for the 920. although x58 (LGA1366) motherboards are more expensive now, they will be able to support the new six core Gulftown chips coming out next year. you will have more upgrade options later on with the LGA1366 motherboards.
 
If you're not using multiple GPUs then X58 chipset is overkill UNLESS you want to move to the 6-core i9 in the future.

If you DO then I'd recommend the Asus P6TD Deluxe (the "D" is important) or the Asus Rampage II Gene - Bluescreendeath mentions the P6T Deluxe V2, I wouldn't bother because the P6TD Deluxe is the newer version.

But if you're an overclocker then maybe it's worth going X58 anyway (Asus Rampage II Extreme or EVGA X58 Classified for some serious beans) until the Foxconn socket on P55 debacle sorts itself out.
If you DON'T then I have no idea other than going with an Asus board - P7P55D maybe?