Fans.
There are quiet fans that have vibration assorbing silicon mounts (Noctua), but they do cost more. They also last longer, coming with a 6 year warranty. They are rated for 150,000 hours, which is 17.1 years.
So you can use the cheap fans that most cases come with, and replace most of them every year or two as they die, or you can get high quality fans, and probably go more than a decade without a failure.
Noctua fans are either tan/brown or black. They run from about $16 to $25 each.
http://noctua.at/main.php?show=which_fan_is_right_for_me&lng=en