A Corsair 550VX has a little more usable power and is better known.
Not wild about AsRock motherboards.
If you are going to use a WD drive, spend a little more and get a Black.
Choose an HSF with a 120 mm fan. It will probably cool better and be quieter.
For a SWAG (Scientific Wild Ass Guess), off the top of my head (but I repeat myself
), I'd estimate the load on a 550 Corsair at around 65% of capacity.