Bunky,
I can assure you that the "Extreme" upgrade to the Tempest is meaningless if you're not using its phono section. I did the circuit board half the upgrade, precisely for phono performance, but skipped the mu-metal power supply transformer half because my hearing's not sensitive enough to notice the hum/noise advantage thereof.
There's NO difference in the high-level circuitry, aside from ability to precisely balance the power supply (trivial). I know because I reverse-engineered it. And there's no sonic difference, either.
--Karl