You are also giving that sub about 500 watts more than it's rated to handle. You need to listen for stress. Can't just assume that since a shop set it up on one track it's set correctly for every situation.
Didn't say it was clipping, said it's a possibility. And depending on audio source being used, and quality of recording, your volume dial needs to be adjusted accordingly to each track.
You've got a lot of money tied up in some good equipment, don't want to see you continue to burn through equipment and money. Rather see you enjoy your system.
And if you do buy a new sub, my vote goes ICON.