Zaikesman, good point. In fact, my Classe CP-35 doesn't even have an on/off switch on either the unit or the remote -- it's on all the time. I have measured it, it uses about 7 watts continuously, about like a night light. I don't think the 47.5 has an on/off either, but I'm not positive.
I have listened to the 47.5 and really would like to have one, but I have not heard the other preamps you mention. I generally like the Classe sound (just ordered a CA-200 to go with my preamp), which I consider to be less fatiguing and more involving than other solid-state gear I have heard. Others consider it dark or imprecise -- there are quite a few threads here on the Classe sound if you do a search, it seems to be a "love it or hate it" thing.
Given that you are coming from a tube pre-amp, the Krell isn't a very likely candidate. You may find it harsh, especially paired with the Krell amp (I say this based on reputation rather than listening). The Classe is generally considered more tube-like than much SS gear especially the Krell (and this has been my experience when I personally compared the Classe to other non-Krell SS gear).
If possible, let your ears be the guide.
Folks here are also quite capable of suggesting other alternatives, perhaps you want to post a more general question about "tube-like pre-amps" assuming you are happy with the current sound. Some searching will turn up existing threads along those lines also.
- Eric