Charlie;

Remember the 12AX7? There was a low noise version 7025. Why do I remember such things? Seems like most tubes are made in China today. I got up to a pair of 813's on one of my amplifiers. Think it was a couple of hundred watts in class A. You could push it to a KW in class C. Not a good idea though unless you wanted to break a lease and blow your speakers.

I would have to study the design of a single ended amp - my approach would be to build a dual ended amp which would have lower harmonic content. Perhaps designs have changed since I was involved with such matters.

Tom