Its interesting.. with the Musical Fideilty X-Can v2 I have....I seem to be turning it up from 11 to 5oclock..all the way up without much increase in output.
I'm looking for an amp that has a good amount of power for the lows and can tame the highs some and strong output.. because the highs can get "tinny" or screetch sometimes. I tested it against the Kef M500 last night. The Kef is much easier to drive and I have to change volume output to 60% on my laptop vs. 100% with the HE-400 unit (Using Razer Surround program I downloaded to simulate surround). Using my Musical Fidelity it was more like 40% output on the Kef vs. 80% output on the HE-400 (using RECON3D for surround). The result was obvious.... When I used numerous tests from Dolby, tests from youtube, that were a wide variety of tests from different manufacturers), the HE-400 had a much larger soundstage and depth. For example, on the helicopter going around your head:
Kef sounded like the helicopter was literally a foot from you going around your head, except the rear pan.. that sounded like rear right, then it hit my head, then rear left.
HE-400: Sounded like helicopter was maybe 10-15 feet all the way around me. The rear pan was much more realistic..not perfect.. there was a small hole right behind me, but much better.
The Kef is a much different design. Both sound great on music, but I am using these for movie watching only