1) The i7-3770K comes with a stock cooler, it is sufficient to keep the CPU cool at stock clocks. You will need an aftermarket CPU if you plan to a) overclock and/or b) want to reduce noise levels (the stock cooler can be noisy).
2) How much RAM depends on what you will use the computer for.
$20 @ Newegg
4) If you're only ever going to use one GTX 680:Rosewill Capstone-550M
($80 @ Newegg)
If you'e going to SLI in the future:Rosewill Capstone-750M
($105 @ Amazon)
Reviews for the Capstone series:http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=266 http://www.hardwaresecrets.com/article/1584 http://www.techpowerup.com/reviews/Rosewill/CAPSTONE-750-M/