How much power does my pc build need?

You are good on power.
I would be hard pressed to pick any parts significantly better.

Personally, I will not build again without a ssd for the os.
Consider using a 120gb ssd and deferring on the hard drive. It will hold the os and a handful of games. 240gb and you may never need a hard drive at all.
A ssd will make everything you do feel so much quicker.
Samsung and Intel would be my picks.