Just thought I'd post an update. I've isolated the noise to one of the 170's. I still haven't figured out exactly where the noise is originating. Every time I think I've got it it moves. I've heard the noise on several different pair. I've even pulled the bridge clips and tried finding the noise on equip. side of block. Due to intermittency of noise it's proving to be quite a challenge.

Again; Thanks for input.