I too am skeptical that the Luxman doen't provide enough bass. So I'll make a blind suggestion, which may not be the answer but is something to look at.
Every amp has different power requirements. It is possible that whatever power cords, power filters, etc you have feeding your amp are adequate for the old amp but not adequte for your new amp. If there isn't enough instantaneous power availble it will show first in the bass. This has nothing to do with the nameplate ratings on the amp and conditioner.