Hi again to anyone that was interested in my problem back then(or now). I have not gone any futher with any testing.
While I have watched a lot more movies using the system, I have not done much more music listening. I have only recently added cables for DVD-A and hope to get back & try some more testing using that format.
I have not tried BB4TB's testing advice butI still think that I will install a fan for the 770.