I think I may get it (BTW, thanks for the help everybody - my friends and family all think I'm some sort of audio/video genius due to the knowledge I've absorbed here in the past year ). If I were to disconnect the RCA plug from one end of the coaxial cable and reconnect it (sans the outer layer of metal shielding) I would break the ground that exists on that line. The sub would then ground itself via the power cord and the humming should stop.
Any special tools needed to reconstruct the end of that cable?