Heat heat and more heat??

Al, the reading at the two RCA's is 0.4 ohms, same as at the two xlr's.
I took the caution of replacing the battery in the meter today ( even though apparently the old one was ok), which seemed to slightly solidify the readings, so I re-took the reading at the left xlr and rca ground, it fluctuated a little but I suspect the true reading is also 0.4 ohms. Seemed to float around there.

Sounds good! So pin 1 on either XLR connector should be a good point for connection of the black wire from the sub.

Best regards,
-- Al

Thanks again Al. As soon as the amp comes back from the factory, I will connect the sub as suggested. Appreciate all the help.

In the home environment, where I am running cables that are what...1.5meters typically ( and VERY well shielded) I just don't get it. The extra expense and hassle for balanced..why??

The reason for this is that balanced connections (if done correctly as they are in a stage environment) will sound better even if the cable is only a meter long. The balanced line system was devised for the purpose of eliminating cable artifact (which allows them to also be longer lengths).