What I mean to say is that if you buy a quality PSU, you don't have to overrate it compared to real power consumption. Also you should't because it hurts efficiency. Even if you would run SLI sometime soon, 600W is still overkill.
Oh, and also the hard drive, I would recommend a Samsung Spinpoint SP2504C because it's a good performer and cheaper too.
The 8MB / 16MB cache hardly makes up for the price difference since the drive cache size doesn't seem to make much of a difference in real world performance. (There is a MUCH larger cache in the OS anyway)
OC newb - your first link doesnt work, brings up a selection of RAM options.
Thoughts - I agree that 600W is overkill for your system. If you truly intended to overclock, you would not be using the stock heatsink (assumption here, since no special heatsink is shown for purchase).
For PSUs, suggest you start here: http://forums.extremeoverclocking.com/showthread.php?t=...
Very good advice on power consumption and what power you will need. A 600W+ PSU does you no good if you only consume 350W on average. In fact, running a PSU at such a low rate is worse for the PSU. Optimal is getting a PSU you will push at 70%, with room for spikes when you need it.
Nforce 5 - I am waiting for this b/c I have the time. Otherwise, I would recommend the Gygabyte you have or the Asus P5B basic.
HDD - Raptor had a killer rebate recently on the 150GB 10K for $50. Not sure if it is still available, but worth a look if you have the extra $100.