I was asked to build 6L6 monoblocks for a very keen tube collector. He would provide the tubes and I would build the amps. Monoblocks are almost double the work with two power trannies and filtering circuits. The requirements were also to use Silk OPTs from Thailand. I chose 20W models for a 5W amp. Interstage caps are Mundorf Evo oils. RCAs are Palladium.
These austere looking smart amps produce deep articulated bass, grounded detailed and rich midrange and crisp highs. Chassis are Hammond steel with wood cheeks and are difficult to drill but worth the effort. Hammond power trannies and 300uf of filtering in a double Pi config produce a very low noise (1.5mV) amp which plays plenty loud. Definitely one of my better and more expensive builds. You are rewarded, though, with an exceptional audio experience.