I'm just going to throw out the Coolermaster Hyper 212+ because . . . yeah. I think we all know why I'm throwing that out there.
Anyway it's not hard to find that HSF for $35 or less. I think Overstock has it for $33 shipped, and if I'm not mistaken, you could get it from Microcenter online for $26 (but you had to look hard for it).
Anyway, it'll outperform the stock HSF and probably make less noise. The thermal paste (TIM) that comes with the HSF should be just fine for someone who is not overclocking.
edit: undervolting IS awesome. Give it a try, especially once you have selected an aftermarket cooler that meets your needs.