Mareri031, Before you start spending money on other parts of your system, take your Pass INT-150 over to your friend's house and substitute it for his Onkyo amp. If the sound quality doesn't improve, there is a problem with your amp.
If there is a problem with the Pass, contact Pass and they can probably recommend someone to repair it near you.
If there is a problem with the Pass, contact Pass and they can probably recommend someone to repair it near you.