RAM, check out the twinMOS (the second link I gave you). That is good cheap RAM, and for the future, if needbe, it'll overclock very nicely. AND it is only $84 I think. As for the PSU, most people will tell you differently, but the PSU that comes with the case will be fine for the beginning. Just make sure it is at least 450 watts. If you want a good reliable PSU though, I think thermaltake ones are good, but I don't have much experience with PSUs. I wouldn't worry about it right away with a tight budget.
As for cooling. Make sure you have at least 3 case fans I'd say. You'll probably want a side fan that is preferable 120mm for intake. You'll also want a front and back fan (80 or 120 mm) with the front as intake and back as exhaust. If you can, get a fan on top too set to exhaust. Processor cooling. I've heard good things about the zalman 7700 cu (i probably slaughtered the name) and I use the Silent Boost K8 which it says is made for Athlon 64 processors. I have an overclocked processor (from 1.8 GHz to 2.3 GHz), and on a cool day (without this bloody hot weather) I am idle around 35 c.
Answer all your questions?