I use an 845 SET putting out 17 watts into Living Voice Avatars. I like all music, but if anything have gravitated to Opera and large orchestral music with this combo, they sound glorious. If you have tube friendly speakers 94db plus, with no dips into low impedence, IMO 7 watt 300B's will do fine for small scale Jazz, chamber music etc. A 17 to 20 watt SET will be perfect for the larger scale music, with appropriate speakers. Of course more and more manufacturers are bringing out "tube friendly" speakers. Look at the interesting industry SET review on www.6moons.com
I am not saying the SS super amps won't give you better base, perhaps dynamics, but they can't give what a SET will.