Added to that, my aforementioned 40GB IBM weighs 560g and feels lighter than my ST340016A. Maybe the 1-platter Baracuda Vs/7200.7s and later are 544g but not so for the Baracuda ATA IVs and earlier models? And yes, I have noticed a huge increase in the volume of sound filling a room when more than one fan is used inside a case, even if it's just the graphics card fan. I find that heat exhausted outside the back of the case depends on a few things: one, PSU efficiency. A PSU that is 80% efficient or more, so long as the case isn't warm and so long as it is well designed, probably isn't going to throw tangible heat out the back. A PSU that is 70% efficient or below will, though, because it is clearly wasted heat (wasted power).
EDIT: I think you were right about the IBM Deskstars 120GXPs weighing more than the Seagate Baracuda ATA IVs.... I picked them up again and the Deskstar feels a bit heavier... and I noticed a -+10% note on the weight specification of their datasheets.
EDIT: I think you were right about the IBM Deskstars 120GXPs weighing more than the Seagate Baracuda ATA IVs.... I picked them up again and the Deskstar feels a bit heavier... and I noticed a -+10% note on the weight specification of their datasheets.