I would find someone to build a dyna(low-mid-hi-mite) before the B22, but there is enough misinformation here that its worth talking about it.
Are output caps better than not? Historically the circuit that the rusidstor amps are based on MUST have both input and output caps. A B22 requires no coupling caps in the direct circuit.
What does rating the distortion "at average levels" mean? seriously, come on, average levels? Average for who? That is not a measurement, that is deliberately being vague. Post up distortion graphs at the same levels (set by voltage) into 32 and 300 ohms like AMB has on his website. Even at "average levels" the 010 does not touch the B22 (at an absurdly high output) for distortion.
I have only heard 3 or 4 B22's, but none have hissed audibly. Can you say the same for rudistor amps?
Regarding shielded transformers: mount them in an external enclosure and put it 3 feet away. Or get shielded transformers AND mount them externally, they are not really that expensive.
Yes, you do have some decisions to make when you pick a B22 as an option, but most builders should be able to explain what advantages they have. The only choices you have with a rudistor amp are model and color! If you want special resistors thats too bad. If you want a different bias point, too bad. If you want different coupling caps, too bad.
to answer the Q asked by rosgr63
The 3 channel topologies have slightly lower distortions than the 2 channel designs, but the 2 channel amps are less expensive to build. I do agree that finding a builder can be tough, but they are around. Perhaps Thrice when he comes back around.