Mr P. I find the treble to be pushed back in the sound stage and less prominent when compared to my A21 and Class D amps. There is also less air in the treble but there is also no grain. I have tried various tube combo's and some are better than others. I have 0.6 ohm resistors in my Maggie tweeters which I will remove this weekend which will help by increasing the tweeter volume by about 1dB.

Bill, your 150.5 will sound different than the X250. The 0.5 series has a different sonic character and is supposed to be more refined. When do you expect to receive the amp?