If if everything is properly connected and working properly including broken in as you alluded to earlier then it just may be that is not the right amp for that particular user.
OP it has nothing to do with quality of ARC gear in general FWIW. All ARC amps are different and this may just not be the right one for you if things continue as is currently. Break in of amps and speakers is a real phenomenon. Maybe that would help. If not consider a different amp for comparison. Something high power and high current. I’d recommend Trying a newer high quality class d amp if it comes to that. Give the Luxman a shot if not already. That might do just fine.