Dionysus, I would buy the Copper amp in your case. The PM-3 sounds well with the AK380CU alone, but it is better with the AK380 amp (tighter bass, clearer mids). More difficult to drive cans simply need the additional AK380 amp. Ist balanced output has 4x the power of the AK380. This is simply needed with cans such als HD800(S) or HE-1000. I have compared it intensively with ALO CDM (which I own too by the way) and Chord Hugo. The Hugo has punchier bass, but smaller and less precise soundstaging, less detailed mids and especially highs than AK380Cu+CuAmp. So technically the Astell & Kern flagship is superior to these portable alternatives. If you like tube flavor, you may be more even more happy with ALO CDM, but it is not "better", just different.