I was finally able to check the amp by itself and the woofer by itself and still at a loss for what is causing the hum. Here are my findings:

With amp disconnected from woofer and powered up and volume turned to 10 the amp does not make any abnormal sound (LFE disconnected)
With amp disconnected from woofer and powered up and volume turned to 10 and LFE connected the amp does not make any abnormal sound.
With woofer directly wired as a front speaker it plays without any rattle or abnormal sound.

The problem appears to be a function of pairing the amp with the woofer.

I have sent additional notes to Outlaw, but not sure what is the root cause now.