PS there are a few ss amps that cater to the low power market, but most systems fit into the above 2 categories. I'll also add that there is another emerging category--the high power tube amp aimed at the 90dB sensitiveity speakers. While not bad, SET fans are not on board.
Hardly an "emerging" category.
Audio Research, Balanced Audio Technology, Manley Labs, Conrad Johnson, Cary, Jadis, are just a small sample of companies that made or make high power tube amplifiers. Some very high poser.
Some of these have been around since the 70's.
And many sound incredible. In a way, the best of both sonic worlds; tube silkiness and solid state heft and dynamics.