Which high power SET

Edoit,
That's a very nice list you have. There's a Shindo GM 70 SET available here on audiogon, surely a fine mate with your Masseto. Yes, some excellent choices to pick among.
Charles,

You could go PSE, Parallel Single Ended if you want/need higher power. Possibly not as pure as true SE, but opens up more choices for amps.

You might consider Japanese Triode. They have a nice TRX-M845 SE amplifiers. May be a little to much to spend to drive your Harbeths.

I own Cary 805 monos which are also probably worth a listen if there's a dealer in your 'hood.

i owned a wavac 572 years ago w/ watt puppy6s. bass was always an issue, clipped a lot, but never had that midrange tone in my room before.

haven't since either. and i'm still trying.

volume pots in signal path are best removed. found build quality was fair at best, and also had a burned wire requiring a fix (really amps are simple enough circuit anyone local can fix it). cary being in states would matter to me just in case...