Lastly, is it possible to use a pair of 650W PSU instead of one big one?
Got lots of smaller 650W PSU's made by Corsair and SeaSonic, a high quality 1000W is a C$200 bill I don't really want right now.
Yep, it's possible. Due to lack of power I connect in parallel 2 PSU's. One is XFX 750W and another one is Antec 750W. You can buy on EBay appropriate connector.
Another solution is to do connection by yourself like I did (because still waiting for this fu...ing connector to arrive from Korea).
You should connect green wire from 24pin connector to both PSU's and one of black wire in same manner. I put switch between those 2 wires to start or shut-down PSU's. Than you can use PCIe rails on your C1 from both PSU's. It's work great since day 1 for me.
Sorry for my english, but I hope you got idea.
Best regards.