I have T1s on the ST on highest gain. At about 50% power they are basically too loud to listen to comfortably. I think you'll have enough power. A lot of people who have been having issues with sound power have found they have a software setting somewhere that's limiting the volume.
What is the T1? What impedance are they?
From what I've seen about people recommending the 250 ohm version with the STX isn't due to volume but rather sound quality and bass response. Not really sure what to believe though.