The amp has approx. 150 hours on it now. It took about 90 hours before the ultralinear mode began to develope some dimensionality with a reduction in grain. At the 100 hour mark, I replaced the stock 18 gauge cord with a Nordost Brahma which didn't seem to make much of an improvement. I changed to a generic 14 gauge cord and the sound improved markedly but I still felt the bass to be light weight. Compared to the VAC, the 120S was more distant, dynamically less expressive, listenable, but basically boring.
I have all components plugged into a Nordost Thor and for experimental purposes I connected the 120S into the wall bypassing the Thor. Wow, what a difference! I believe it is safe to say that any Nordost power product is a poor match for the 120S. The system now has deep solid bass and the dynamics are much improved. The treble grain is virtually gone as well. I'm still using the stock tubes and I have had no reliability issues whatsoever. I'll need to find a better PC than the generic 14 gauge unit I have now. Perhaps there is more to gain from this amp.
I will recant my initial criticism of the ultralinear mode now that it has sufficient hours and Nordost removed from the power supply. The triode mode is still too laid back and mellow for my taste.