I know it has been a couple months since the last comment in the thread so my thoughts may not be helpful as you may have made a move with new gear already, but I agree the Hegel H390 is not a soundstage champ and the reason I sold mine. The quality of sound was good but everything sounded as though it was coming from the center between the speakers 90% of the time. To experiment I used it in HT Bypass mode and connected a Parasound P7 preamp using the same DAC that was going into the Hegel and all of sudden my speakers (Monitor Audio PL200II) opened up in all directions and finally disappeared for the first time as they are relatively new. There was some added treble harshness with the P7 in place but it proved the hegel has a pretty restricted soundstage on it's own and my Denafrips Pontus II 12th has a larger soundstage than the H390s internal DAC.
I auditioned the moon 330a yesterday and can confirm it has an incredible sound with a big expansive sound stage, but the 400m may be the way to go with more power and most likely an even larger and more defined soundstage. Those series moon amps have high gain so match them with a low gain preamp like a Pass Labs XP12 and it may be a match in heaven!
Good luck on your gear journey.