Also need to consider what frequencies are actually being produced and how audible they are. High pass filters do wonders for making sure power gets used in an efficient way.
BTW, my WB100 replaced a valve-pre (Ampeg SVP) and a 460W Mosfet power amp. I play in a loud band. Two heavy guitarists. Tone is different with the WB100, but I don't struggle to keep up any more than I did with my old amp. In fact quite the opposite. Grit, grind and clank would be all too easy. I play a P with the tone sometimes rolled completely off and use flats. I like a good, thick, warm and meaty low end, with a little bit of sizzle on the top, which is a particularly power hungry tone. I sometimes use a high pass filter to get that little more juice out of it sometimes too, but not all of the time. If I put more mids into that and drove it, nobody would be hearing a drummer. It would be earsplittingly painful.
One caveat is that when I changed amp, I also changed cab from a Gen II Barefaced Compact to a Gen III Barefaced Super Twin, so there would be a db increase there.