I'm looking to do a 5 card rig and I'm a little stuck also.

I've ordered 5 770x cards but,

1) I don't know what motherboard to get (gotta admit I'm a little confused by what to do where and how on the MSI 277A-G45 - skipped too many EE classes maybe, may be just plain stupid, not smart enough to know which...)
2) how big a power supply I'll need (1000W maybe? 1050W? even bigger?).

Thanks ya'll!