Denon Mono block amp running hotter than the other

I have a pair of Denon 6600A mono blocks which one is cool and the other quite warm but yet sound the same and have what appears to be equal volumes-any ideas what may cause this should I be concerned?
I had a similar situation once with a Classe amp where one side was much warmer than the other. I had the amp's bias adjusted and the temp difference was gone. As far as I could tell there was no sonic difference before or after bias adjustment.
Before sending both amps in to find out which one is correctly biased and which is not, consider this.

They may be biased the same, but one has to work harder than the other. Could be for many reasons, but before we go there, just swap the amps with each other and see if the hot one stays the same. If the heat follows the amp, then send them both in for calibration.
hi, wow poa6600a dennons, what a blast from the past, they were one of the first pairs of monoblocks I ever owned, back in the early 90s and I was in my early twentys. seems like forever ago, I wish my hearing was as good now as it was then. oh well, how long have you had them ? the problem sounds like runaway bias, I think you can get that fixed. good luck, chrissain