The eXtreme PSU calc
puts you at 306W min / 356W recommended so the 620W is overkill but will work just fine and last through several upgrades (or generations for that matter), it's a killer deal I picked up one of each (a 400w and 620w) myself this weekend too.
The k-series is screaming for some z77 for OC potential, I usually use the b75's for budget i3 or pentium g-series builds. You could, get the non-k series i5 and bump up to an h77 for a more balanced budget build, and for most quads I throw in a cooler like the hyper212 just to keep quiet coolness when the load demands rise.
I am sure there will be other suggestions, cheers mate