So for speed the 640 > 1tb, but if space is that key get the 1tb, though I don't think you will fill up a 640gb drive
PSU, you could go as low as an 800watt PSU, but I wanted to give you something that would give you plenty of head room on the OC.
EVGA and Asus, if you go with a Nvidia chipset (which I don't recommend, they aren't as refined or stable as intel's) then the EVGA 780i FTW is superb.
i have to agree about the nvidia chipsets.
Go for a wd 640gb.. very fast drive.
For the heatsink, HDT-S1283
Yes, the 1000w is a good PSU, xigmatek PSU's are very good.
I suggest a antec 1200 or 900.