I haven't built an amp in a long time and it has been something that seems to bother me as I am not short on ideas but rather time. To scratch that itch I was thinking of doing a relatively simple build using a tube I have many of, the 12BK5. It is an orphan tube, developed to be used for service as in TV sets, in SE it only needs -5V bias so +/- 5V to drive it to full output. Could use an opamp to do that. Maybe a 12AX7 through a tone stack will be able to drive the outputs to a reasonable level.