HDD: The F4 is a good choice, but I also like the Spinpoint F3. A 1 TB drive is only $55 on Newegg (with a promo code). It's a touch slower and a little louder and such, but it's a great drive and you can't beat the price per GB.
PSU: I trust Corsair, but I don't know much about their "Builder" series PSUs. I do know Corsair recently released a lesser quality 650W, which I assume is the GX. Instead, I'd proabably pay $5 more for the Antec Earthwatts 650W, which I know is high quality.
HSF: Don't bother with a cheap water cooling solution. Instead, get a great air cooler. They'll cool just as well, but without the potential mess of water cooling. Check out the Notcua NH-D14 (usually about $90). It's easily the best HSF out there, but it's pretty big. If it won't fit in the HAF, check out the Scythe Mugen 2 Rev. B (SCMG-2100 on Newegg I believe). It's only about $35-40. I'd probably go with the Scythe to save some cash for the next change.
CPU/Mobo: Not great choices. First, the X4 955 is the exact same CPU as the 965, just without a very slight factory overclock. Second, that's an older board. I'd look at the ASRock 870 Extreme3 instead. However, even with all that, I'd take a long look at the new Sandy Bridge CPUs. They're a lot faster, and not that much more expensive. The i5-2500K is about $225 and a good board (the Gigabyte GA-P67A-UD4) run about $190. You'd easily get an extra 40-50% performance for about the same percentage increase. To be honest, I wouldn't want to buy any non-Sandy Bridge CPU right now.
Well, it kind of depends. Are you planning on Crossfire? If not, you could probably drop it to a 550W model (stick to Corsair, Antec, Silverstone and SeaSonic) and save a bit on the board (the ASRock 770 Extreme3 for AMD, no idea on a specific model for Sandy Bridge). If you are, 650W should be enough, unless you're going for a really massive overclock on everything. For most purposes, the 650W should be enough. If you don't mind spending more, the Earthwatts 750W model is about $80.
I'm probably not planning on crossfire, I think ill be using one gpu for the time being. I also change my cpu and mobo I decided to go with the sandy bridge i5 2500k and the gigabyte mobo. I also change the gpu from the 6850 to a (MSI N460GTX Hawk GeForce GTX 460 (Fermi) 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP).
The 912 is suprising void of fans (it only has one), but there are other great choices in that budget range as well. I like the Rosewill Challenger, Rosewill Destroyer and Antec 300 Illusion personally.
I don't like recommending cases that you need to buy extra fans for. Generally, once you've added the cost of the extra fans (typically $10 a piece), you could have easily bought a better case that already has more fans.
I keep finding that the Antec 300 Illusion is pretty amazing for it's price. It's high quality, it looks pretty good, and it comes with three fans already.