A few people have mentioned specifically "cheap" fans. Don't buy cheap fans. They are loud, get louder as they die, and they die quicker. LED fans aren't necessary, but at least buy some decent Zalman fans or something, it's like a $2 difference and they'll last longer.

Also if the poster is still considering their build: a good case and proper maintenance are crucial for keeping temps down. Get something with a nice 120mm outlet fan on top (Antec, ThermalTake, CoolerMaster, etc.) and something with filters. Filters are key, because they get caked with dust and your computer internals don't, otherwise you should be up in it's guts every couple of months with an air-can and get the dust out from your fans and between your heatsink fins. I've seen as much as a 5 degree change in temperature over the course of a couple of months due to dust.