Corsair AF120 quiet edition for cases and SP120 quiet edityion for radiators. They are black, come with interchangable red, white, blue, rings, the quiet edition runs run very quiet and get good reviews. You can buy them in 2-packs. Not super cheap, but for quiet and good quality, cheap doesn't work. A $5 cheap case fan either won't move any air, or will sound like a 757.