Well a few problems I see with the build.
You selected the T1 Revision of the board. I recommend the A1 Revision if your going for max overclock on the Q6600. The T1 overclocks well but most seem to have slightly better results with the A1 Revision.
Second why a Samsung drive? Go with a new Seagate with perpendicuar recording or a western digital. Your on the right track with the 16mb cache. Size is really a personal option. If moneys tight why not just pick up a 320meg or something a little bit cheaper and shave a few bucks. Then buy a second media drive when you have the coin.
Alot of people like the Corsair ram never used so I can't quote but I will say I love my G.Skill Highly overclockable. You could shave $50buy picking this ram. Lower timings less money and highly overclockable. I have not fine tuned mine yet but people seem to be overclocking to 1000mhz easy. Link
You could also drop some on the PSU as well. Thats overkill for a single 640GTs. Although if your going to upgrade to SLI that would work out better for you. If not look for a good 550watt with a high effciency and solid 12V rail.
You could probally also save some coin if you had some CD/DVD drives you can just swap out and use until you have money to get new ones. If not that DVD drive looks fine.
A tip with newegg also select price watch and have them alert you of price drops on items your interested in. That ram I linked you to is normally $114.99 maybe a weekend special or something.