A sonically excellent power amplifier should exhibit high input impedance, very low output impedance, flat frequency response, and ultra low distortion. And it should do all of this without contributing any extraneous hum or noise. In addition, it should also be capable of producing unclipped power output that's some 2 or 3 dB more than your loudspeakers can tolerate.
It first became practical to build a power amplifier that meets all of these requirements back in 1976, when PNP silicon power transistors finally became affordable, thereby permitting fully complementary differential solid state circuit design at reasonable cost. And that's when I personally left vacuum tubes behind, in the past, where they belong.
While it's theoretically possible to construct a tube-type power amplifier that will approach the described design criteria, that product will exhibit persistent vacuum tube degradation that begins at initial turn-on and ultimately ends in cathode depletion failure—barring other modes of premature demise (e.g. open filament, vacuum leaks, gassing, microphonics, atypical distortion, hum/noise). So vacuum tubes are not a wise choice when stable, long term circuit performance is a serious design goal.