You're really wasting a lot of money on that power supply. It's way too big for what you've got.. One of those PSUs could run a GTX 295 in SLI, I think. Your electricity bill will also have a 'knock-on' effect. :P
I'd lower that to a 750W.
YAY. You bought the same CPU as I did, I've got the D0 stepping edition too. I won't be overclocking it though. I haven't used any thermal paste on my CPU fan/CPU, because I think that the fan that came with my 920 had thermal strips already on it. It's probably some really cheap and crap thermal material, but no matter.

I've got a 256GB SSD, and well, I guess you get what you pay for. My OS boots within seconds. Despite this, my advice to you would be not to purchase an SSD. Once the prices go down, and they come in bigger sizes, you should buy one.
An ATI 5970, or the coming GTX 300 series would be a great upgrade to your card. The 5970 is really future-proof, as it has DX11. You'll be fully equipped to play all the games you want for the next couple of years with that DX11 card.
Personally, I'd leave the RAM at 6GB. Upgrading it wouldn't really make a huge difference as there's only so much you can do, which you'd really notice. If you're building this PC for gaming, 6GB is more than enough to last you forever. D: