I just bought a used, 10kg (22lb) single-ended 7wpc Musical Paradise MP301 Mk3 tube amp, and it's on the way from Florida to Panama right now, but for me, I really only decided to buy it for sentimental reasons. It will probably sound Just fine for most of my listening via my small speakers in a small room. My only source is mt Daphile/LibreElec (Kodi) "HYPC" via a Topping DX7s DAC with a volume control, so a preamp is not necessary.
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I found it on USAudiomart for $425 including shipping to my forwarder in Miami. It has an auto-bias feature, and can accommodate 6L6, EL34/6CA7, 5881, KT66, KT77 and KT88 output tubes. Although those who talk about the amp on internet forums never mention it, I would assume that only one of those tube types are optimized for maximum performance, or perhaps none - as a compromise for easy interchangeability. Also, it is my understanding that how hard you drive the tubes (plate voltage?) changes the "sonic signature" and affects tube longevity.
The amp includes a pair of JJ 6L6 power tubes plus 6J8P driver tubes, and also a pair of Gold Lion KT77's that came matched and tested from Kevin Deal at Upscale Audio. I will probably also buy a pair of tested and matched Tung Sol 6550 power tubes from Upscale - just for fun.
In a couple of months when I buy the 200ASC/200AC ICEpower modules from Parts Express and finish my 70wpc (8Ω) Ghent/ICEpower amp, I will end up having three power amps to play with. In addition to the flea-power Musical Paradise MP301 SE tube amp and the 70wpc (8Ω) Ghent/ICEpower amps, I will also still have the BIG and heavy 1990's 70wpc (8Ω) Classé Model 70 Class-AB amplifier that is currently installed in my main system.