Oops, I made a boo-boo. The tiny terror has a 12au7 as the PI that feeds a pentode output stage. My bad. So the tiny terror is like 5 times louder than what you propose (watts not dB). The bass response of the tiny terror is still rather thin.
Either way, with a mini tube - socket output the 12au7 and 12bh7 sound close to the same as far as tone, the bh7 gives an extra watt of clean output if you bias it up. The ECC99 has a fatter sound to it and gives you another extra watt. Doubling any of them up in parallel pairs works well if you have an extra tube and socket. As always, make sure you have enough iron.
My son is right in the midst of a project like you're thinking about. It has evolved from basically the schematic you posted to something much meaner. Originally, we ran a 12AU7 as the output, and having a layout so simple proved easy to fine tune the gain stages and tone stack to his liking. The TMB stack got a "mid sweep" control, and the bright caps got taken out. The Eq buffer got deleted. Then he figured out the amp wasn't loud enough for his room.
We turned the 12AU7 into a long tail pair that drives a pair of octal sockets. Feeding upon his ever-changing intentions, we changed the feedback path so now it feeds into the PI, and has presence and resonance knobs. We tried triodes and pentodes and tetrodes as outputs, as well as a dozen or so preamp tubes. He settled on 2 x Sovtek 12AX7 (1-preamp, 1-PI) and a power stage layout that will accept 6K6 or 6V6 output tubes without adjustment. The 6K6 are loud enough for the bedroom, and the 6V6 are loud enough to practice with the band. He voiced the amp much less "gainy" than I expected, deciding on a clean "shiny/tweedy" structure that is more like what you are after than I thought he was. If he wants super distortion or overdrive, he stomps on a pedal for it.
Now when he goes to the music shops to audition amps, he goes straight to the tube amp and half stack section. The modeling and solid state amps have lost their novelty. Some of the pricey tube heads don't even sound as good as his little "lunchbox".