Regarding PSU: I got mine for $5 (I kid you not, 1-day sale, usual price around $40), and it's a 450-watt that's been pretty danged steady since I got it. I dont' have much experience with PSU problems, but this sure hasn't given me any problems.
But I would suggest reading reviews about a cheap PSU before buying it. I got mine off newegg, so I read all the user reviews first, made sure it wasn't a lemon.