Assuming the new amp is not defective or incorrectly setup, it sounds like your new amp is just a mismatch for the rest of your system.
You said you loved the sound of your old system. Can you go back to your old amp? Was the purchase of the new amp in search of something specific or just the attraction of a new toy?
You'll need to decide which is more important to you -- the sound of your music or the gear itself.