Klimax power amps have RCA shield connected to circuit ground which is lightly (~100R) connected to chassis.That is good background info to have, but it is not directly relevant at this point. Corresponding info about the preamp would definitely be helpful, though.
The KDS (the source I used with the earth plug on the rear has transformer coupled outputs, so RCA shield is floating.That is definitely relevant, as it most likely means that the circuit ground of the source is isolated by the transformer from the circuit grounds of the preamp and power amp. Which would absolutely mean that the ground point on the source should NOT be used as the ground point of the sub's input. If that were done it would mean that the return path to the amp taken by current provided by the amp to the sub (remember that current needs a complete circuit to flow) would be mainly via the AC safety grounds of the components + the safety ground connections in the power wiring + whatever impedance connects the circuit grounds and chassis of the components. Definitely not a recipe for good results.
Im taking it in this morning to get fully checked before I go further.OK. Good luck!
Regards,
-- Al