Fmpnd, I had a very similiar problem. The PS1 was the quietest for my transformers. The SS5 was a bit noisy, but not so bad I wouldn't use it. SS1 was out of the question and all the others seemed to lack something. (depth and weight) So I used the PS2 80% of the time.
That became "the" issue for me with the PS300. If each setting was adding or taking something away, it seems to me that I was changing the signal and music. I bought the unit to filter and clean up the power, not as a tone control. I've gone to the Hydra, it's just nuetral, quite and runs cool. It also tends to open up the presentation better than the PS300 at any setting.
I was able to use the PS300 for my amps, pre-amp and SACD player. The presentation was best with the amps included, but the Hydra for my system is a better fit. QUITE!