Need help choosing a PSU and a cooler for my new PC build

[JEMC]

Nice beast!

If you look at Anandtech (with a system similar to the one you have), a 800W PSU will be enough. And as zarx said go for a good PSU, don't try to skimp on it or you may regret it.

As for CPU cooling, it's up to you. All-in-one water cooling set-ups offer the same performance as high end air heatsinks at lower rpm, or better performace at the same rpms.

The Sandy Bridge family are hot chips, even more if you plan to overclock, so you will need a good/very good cooler. How do you feel with the idea of having water running in your case? If you are fine can deal whit it, then the H100 that zarx mentioned seems to fit in the roof of your case, but you can also get other closed WC set-ups from Corsair (H80)or Antec (Kühler H2O 920). If you don't like the idea of water, you'll have to go with a tower heatsink.

And, as zarx says, check for reviews, both from professionals and from users to know more about them (is the heatsink easy or hard to install, how long are the cables of the PSU, noise, etc).

Edit: Here are 2 sites with many cooler reviews: Frostytech, Legit Reviews.