Yes, there was obviously a problem with your amplifiers. Even a 50W amplifier can sound decent on Sound Labs. The CJ LP140M’s you tested probably had bad tubes. The CJ LP140M can take either 6550 or KT88 tubes. I have preferred both over each other at different times over the past five years of ownership. Also, don’t forget about the driver tubes, which are 6922. I’ve switched those out as well, but haven’t evaluated the effect of those tubes to any significant degree.
No, you can’t bi-amp Sound Labs, as they come from the factory.
