Pros and Cons seems a bit on the square side...stereo chassis seems OK to ~20W. L-C power supplies for anything bigger get too heavy to carry easily. Mono construction requires matched stuff. Can't have one channel 40V different from the other.

So, class A output stage. 15-25Watts. No rare or expensive valves. No scary voltages.

This leaves a few possibilities. I am trying to decide on the next amp project. Expanding to 813's for personal use and 'research' is one possibility. Some small, comparatively inexpensive stuff like 6V6's or 6L6's is another. The new 7591's look quite appetizing as well. The ease of driving them is not to be ignored. the question of where they like their U-L taps is probably going to be a somve by building thing. Multiple taps is no big deal with a lot of the designs I'd use for OPT's.

regards,
Douglas