1) Your ram is slow, and while you have a lot of it, 8 gigs is more than enough to run any game. You should get 1600MHz ram or above for gaming.
2) You could get away with a 600watt PSU easily.
3) If you search for your parts on newegg.com you will get very detailed specs about each part. I use this site to buy all of my pc parts simply because of the detailed information they give you about each product.
Hope this helps you out a bit