I want to add a second HD, likely an 80GB to 120GB (depending on price). My system has a 30GB IBM Deskstar which is just about filled. I have a mid-size case (Super Power Polaris II MT300) and a second HD would mount in the slot just above the first one. I am worried that two HD mounted so close would cause problems from heat and/or vibration problems. Does anyone have any advice?