I think the first time I heard an SET amp was the ASL Leyla and the De Capos (the pair that I now own). I guess I wasn't prepared for it; but I really didn't like it. There was definitely something magical in there; but when I say 'in there' I'm referring to the harmonic fog the permeated the entire stage. Dynamic contrasts seemed to fight their way out of the speaker to arrive, spent, at the listener position.
It's possible that there could have been something wrong with the amp? But the dealer didn't seem to think so, and I didn't hear any telltale hissing or popping or obvious overload distortion. Maybe I was listening too loud (maddeningly, I got the impression that setting the volume anywhere higher than about 1 o'clock made no difference at all), but it was a
small room--about 10'x12'x8'. The disc (probably spun on a Musical Fidelity A3 CD player--it was that long ago) was something orchestral, probably contemporary to Berlioz--a good-size orchestra, but nothing too stressful--no bass drums or organ pipes.
Obviously I'm not really an 845 kind of guy. It remains to be seen if I'm a tube kind of guy, at all. If so, I think I will need a good bit more power. (VTL ST-150?)
My room is smallish, 17x11x8...
Although I'm no headbanger, I do enjoy some bombastic ocrchestral at times.
Based on that, (if your 'bombastic' is even half of my 'bombastic') I don't think 3.5 watts is even in the ballpark. I couldn't get satisfying volume (i.e., even bordering on bombast) out of the de capos with 22 watts in a room smaller than yours.
But, I run my De Capos with 150 watts, solid state. I am not entirely happy with it, obviously, but I passed over pretty much the entire ASL line when I bought it. The set of compromises I wanted at my price point was very different. I sometimes/often listen to fully-orchestrated romantic symphonic music (i.e. Mahler, Bruckner) as well as bandwidth-enhanced, dynamically-challenging music from the 20th century, from Anthiel to Stravinsky to Radiohead. My room is of a reasonable size--similar to yours. (see my system.)
I have definitely heard great results with single-digit amps, but they have all been with truly high-efficiency speakers. The SAP full-range two-piece boxes (I believe it was their Quartette) at the last Montreal show sounded great with 6 watts. (Sorry--I can look up the models if anyone cares.) Their efficiency spec is 95 db.
The point to all this is, your mileage may vary. I know there are a lot of people very happy running De Capo's with single-digit-output amps. I would definitely try at home before buying.
brucegel: What is your take on this? You've mentioned in the past that you can play as loud as you like with your TT-25's. Is 25 watts vs 22 watts that much of difference, or is there something else going on here?