First off, DONT buy precut dampening mats. They have too much space everywhere. Buy the mats, cut them for yourself and fit em in every small inch you can find. I did that with a case once and it was just unbelieveable how quiet it went. Even my extremely loud U160 SCSI HDs were barely noticeable after that, and before my whole desk vibrated because of em. I didnt even dampen the HDs themself. After that I bought a precut set for my new computer and it was nowhere near as silent as my self-cut one. Secondly, buy tar mats! These weird carpet or felt ones are crap! They dont dampen near as good as the tar mats or tar mats combined with rubber foam. There is a reason why noone uses carpet/felt in car-audio applications. They use tar directly or tar mats or something that is similar to tar.