Actually, for AMD processors, the standard heat sink and fan that comes with retail purchases work great. Try searching websites for AMD's heat sink and fan (they are under $20). I recommend that you shell out just a little more and get a better one though.
speed control lets a fan slow down when the temps aren't so high... when you're just surfing the net or listening to music, when loud noise is most annoying. when the cpu is under load and the temp goes up, so will the fan speed.
good point... i've thought about that, myself. wouldn't placing something like dynamat on the inside walls of a case help with sound? well, dumb question, i guess... it would have to... that's what it's for.
might go buy a few squares of it and try it someday.