Just an update. After speaking to one of the techs from Axiom, I decided to purchase a ground loop isolator off Amazon. It completely eliminated the hum. The sub is a nice addition to my system. The isolator may have cost $100, but thanks to Axiom's Black Friday sale, I still came out ahead.

"Not throwing my hands up or my dress above my ears don't mean I ain't awestruck." Al Swearengen