When I wrote "best mobo for i" google suggested "best mobo for i5 3570k" as the first thing, try googling that yourself, that is probably what most people replying to this thread will do for you.
Well, I'll answer you anyway: Gigabyte Z77 GA-Z77X-UD3H ($400)
Motherboards doesn't mean that much, so you don't need to spend $400 on one. You can get some great ones for $200.
As for how many watts power supply, i assume, you need, 500-750 would be enough.