Counterpoint 5.1- Beyond My Comprehension

The 5.1 is good as it is as long as it's stable. I wouldnt sink money into it unless there is some sentimental value.
There's really nothing special to a dual 6922 grounded cathode parallel plate-drive line stage. An SA5000 with the followers pulled is essentially an SA5.1.
The Phono stage is a 2 stage 6922 with grounded cathode. Really nothing special.
The Power supply... The section after the 6CA4 rectifier could use a choke. The tube regulator section is in the main chassis I recall and without a service manual I wouldnt start working on it.
you can just do a signal path mod by changing out resistors and coupling caps (the output cap will be smaller, less bass, after the mod as I recall it uses a 10uF RelCap. Modern high end caps are 10x the size)

If you want to get it up and running either email JWu or myself from the Alta Vista website. JWu is in CA and I am in NJ.

You may also want to mod the power supply to a pure tube set-up.

Bigkidz the 5.1 is pure tube rectifier and regulator contrary to whats written on AltaVista. The 3.1 is solid state.
I think even the voltage reference uses a gas tube.

I am looking for some tube suggestions for the RIAA/ Line stage? Any ideas I would greatly appreciate.