I think the heart of the answer is in your second question, the circuit design.
I'm a big fan of Nelson Pass's designs and he uses Mosfets but I have a Bedini 45/45 amp that uses bipolars and it's very sweet also.
I'm a big fan of Nelson Pass's designs and he uses Mosfets but I have a Bedini 45/45 amp that uses bipolars and it's very sweet also.