Did some troubleshooting today;

* Unplugged the TV and sub, still have hum (SHH).
* Pluuged the amp into a different circuit, SHH.
* Unplugged all AV gear from Monsterpower 2600, SHH.

* Checked the grounding of the outlets, good.
* Unplugged all AV cables one at a time, and BINGO!

HOWEVER, the one plug that seemed to possible be involved was a digital optical cable feed fromm DirecTV HDTV Tivo. When I unplugged it, the hum went away for about 2 seconds, then reappeared. Plugged it back in, and it went away for 2 seconds, then reappeared. Unplugged, went away for 2 seconds then reappeared. Pretty consistent.

BAd for me, as the Tivo unit does not have an optical out. And right now I dont have another optical cable to swap. So, off to the store to get another.

I am crossing my fingers its a bad cable.
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Panasonic TC-P65S1 65" Plasma HDTV, Marantz AV 8801 Preamp, Outlaw 7700 Amp, Klipsch RF7 (X-over dean G modded) RC7 (X-over Dean G modded) RS7 CDT-5800C speakers, Outlaw LFM1 EX Subwoofer, Oppo BDP-93, B & O Turntable, Toshiba HD-A2, Sony CD & DVD 400 disc jukeboxes, DirecTV HD-DVR, PS2, PS3, Wii, Harmony one remote, Monster PowerBar 1200 for the TV, sub, PS3, HD DVD and Wii, Tripp Lite Isolation Bar for the Amp, Pre-Amp and other sources.