I have the Diavolo and find it to be very resolving with great bass.No ringing of the tubes and the KR tubes are available from Art Audio or Welborne Labs.They will last several years at least. The PX 25 at only 6 watts is supposed to be the best sounding if you have efficient speakers. I haven't heard it but have spoken to several people who own it and they think it the best they have had.
Call Joe at Art Audio and he'll answer your questions.
Call Joe at Art Audio and he'll answer your questions.