Yes I could tell the difference immediately.
Here is how I test. I have a 10 random songs and play them repeatedly in a few days so I get use to each of the songs. Then I swap the amp and play them the same way and look for improvements in each of the songs.
The ARC 150.2 is a very old amp and current market price is about 1K. It sound good after a long warm up and at higher volume. I also had PS audio stereo and Wyred 4 sound 7-ch in the past and none of them impressed me.
The question is should I invest in a DIY pair of monos ncore 400 (available from hypex late February?) to see if I can get better sound than the NAD M22 or should I not?
I'll have a chance to compare the D-sonic M3-800S as well.