Wow... long time I have since my last "browse" in the Axiom BB... well, it feels good to be read the post again...
I have a T163 as well with an Outlaw 770. I have the same issue. Is your T163 brand new, I mean, the V2? Because mine was the previous model (not V2), and when I send it for the upgrade, the noise that you are experiencing became worst. In stereo mode is very subtle, but is multichannel, is audible in a room at normal listening level (I have friend that did not hear it, it will depend a lot on your ears). BTW, the V2 upgrade allows for bass management, and replace the HDCD decoding card and replace it for the DOLBY PLIIx. If your DVD/CD player plays HDCD, you lose nothing thru the analog output.
I could never get rid of the noise on my setup. I purchase a Monster clean power, and nothing. But I had a mess of cables, and I always tought it was because of that. Plugging the ICBM on the chain just made it worst. I have the EP500, but I never detected the noise on the sub after I loosen the screw on the back plate.
I have to say, that since the upgrade, the noise appeared. Does your T163 "clicks" when changing surround modes? Is a small 'click' I hear when I am not playing something and the volume level is high enough (> -15dB).
Well, I am sorry I did not contribute a bit on solving your issue, but at least you are not the only one with noise on the T163. Maybe arranging the cables/ground/etc reccomended on this BB will improve it.
I havent heard my setup since April (2006) as I moved out of the US and my rig is on storage at my home country Venezuela, where I am neither at this moment. I miss so much my AXIOM !!!!!