My iMac is really hot! That is, when I run my hand across the outside of the machine, it is warm all over, and the entire upper portion of the back is what I would call "hot" to the touch. That is, I can place my hand there for a while, but it is uncomfortable. Is this normal? I suppose there is a specification for case temps. In a more analytic vein, iStat Nano shows component temps as follows: HD: 58 CPU A: 57 GPU: 64 GPU Diode: 68 GPU Heatsink: 64 Ambient: 31 Memory Controller: 58 Compared to what I have seen posted elsewhere, this seems at the high end. Should I be concerned?