zimm, casey01 - thanks for your replies.

zimm - I had started doing some of the diagnostics you had suggested (i.e. re-wiring center channel to on of the mains, playing cable in stereo, etc.) but I just had a new baby (well, my wife did while I watched :)), so I haven't had much time. I'll continue with your suggestions this week when I get a chance.

casey01 - I agree, I get the same differences is SQ and volume from channel to channel. The worst is HD though - the program's volume is much quieter than the commercials. I have to continually throttle the volume on my receiver during commercials (quite annoying).

Does anyone have experience with Shaw cable in the Calgary (and area) region? Do they notice the sibilance with Shaw on their center channel/setup?