The ABM series are fantastic amps but I must say that you won’t get valve tones from amps with only a valve in the preamp ( from my experience)
The RM series and other class D amps sound equally good in my opinion although the ABM600 does have some welly to its sound.
Ive owned full valve amps CTM100, Ampeg V4B Ampeg SVT CL etc and they sound great but I don’t think today are really needed especially when you factor in the weight, difficulty selling on ( shipping ) and potential valve issues ( rare but possible)