Okay - I swapped out the 6080 for a NOS 5998 tested and sold by Brent Jesse (ie, it's perfect) and there still is a balance issue, and sadly, the voltages test the same...
Part of me feels good that it isn't an obvious issue.
Part of me is really disappointed as clearly is something going on here.
To pay $165 to diagnose a $199 doesn't make sense: I would just as soon throw it out and buy a new kit, frankly. Don't get me wrong, I'm not knocking the service, I get that it's a flat rate on a $199 and on a $1999 amp. I also really appreciate all the time and effort everyone has put into this.
Out of interest, what's all between the 1 & 6 and 5 & 10? The big board and the 6080: is there anything else? I am considering rebuilding the big board and replacing all the parts with new as it's really only about $5 worth of stuff on it. I just want to know if there anything else I should be swapping out.