I have a T973 driving Dali Diva Grand mains in a 7 channel setup. I have used a M15 and a T175HD with it. I am very impressed with this setup. I went from a two channel setup to 5.1 then 7.1 and have recently returned to listening to vinyl using a VPI TNT, ET2, Monster Genesis 1000, BAT VK P5 front end. I have not heard anything decent to compare it to recently but I am pretty happy and a bit surprised with the results. I don't think I lost much if anything going from the M15 to the T175HD. I definitely gained from the Audussy in the T175 as I have a difficult room, 20x20.
If you get the T175HD make sure to update the firmware.
If you get the T175HD make sure to update the firmware.