Im not blaming the amp, it is just a 100w amp, and the reason people say about 'valve watts' is that once a valve amp runs out of steam it compresses and distorts with even harmonics which are musically pleasant, so people are happy with that. a transistor based solid state A/B type will distort with odd harmoncs which aren't musically pleasant so people don't do it, so you get this idea of valves being louder, just that valves are more 'musical' when overdriven.
A class D will run out of power supply capability before anything else, so yes, the low end will go first because it is the bit which requires most power.
If I was going to use the CTM for pub gigs without PA support and wanting to not overdrive, I could go for a CTM300, but that would involve having someone to carry it for me, and I suspect that isn't going to happen!