Your Tannoys are are quite efficent at 92-93db, and with a benign 8ohm load, that’s why do don’t need a 250watt amp that can almost keep doubling it’s wattage all the way down to 2ohms. This is the type of amp that you would use on Wilson Alexias with their down to 1ohm at some bass frequencies loading.
By going less wattage you can get amps that are running much higher in Class A bias (which is better for sound) than the Gamunt can. The first watt is the most important so the more Class A watts you have the better the sound should be that’s why i suggested the smaller Pass XA .8 series.
As far as what I read with the Transcendent 300B OTL monos you only have 1.5watts?? Which sounds very low, With the Atmasphere M60 you get 60watts.
Maybe Ralph from Atmasphere will chime in, as knows his opposition and maybe he can explain what’s going on with the Transendent’s 1.5w
@atmasphere
Cheers George