Trex -
I am no expert at all but yes, a line conditioner is a lot more then just a surge control. A surge is just going to clamp power at some predetermined rate and kill itself in order to try to save your equipment from frying during a huge surge. A conditioner is constantly cleaning up the power signal from minute spikes and dips and stray noise that is all residential power. If you ever hook up good test equipment to an AC outlet in your house you will see how poor your power really is. Constant fluctuation and terrible noise in the line. Also you are setting up a single ground for all your devices on the conditioner. For all you know, a bad computer power supply or your refrigerator is crapping junk on to your power line and your sub (which can play 60Hz ((the exact frequency of AC power)) is amplifying that noise. A line conditioner would filter out that noise before it gets to any of the device's power supply. That is just one scenario. Just from your description it sounds like an electrical issue and not a sub signal issue. But who knows.
Many line conditioners also have coax in and out so you can try to clean up a video signal and provide surge control on that cable as well. Some actually filter the video to remove all kinds of stray junk and noise. You can also get separate gear just for the video portion. I think much of Monster's higher end cables are over rated (well, at least over priced). That said, I use their HTS5000 power centers and think they are great. I have used the 2500 too and it was solid. Panamax, Triplitte, Audience, PS Audio... etc all make them but I cannot give you personal opinion of them. I can tell you that my system's overall noise floor dropped to non-existent when I installed the conditioner and my cable is rock solid. Check this page for a lot of reviews
http://search.ecoustics.com/Editoria...r-Conditioner/
Also as BlueX5guy states, long runs for a sub work better with quad-shield RG6 for the reason stated.
As Mickey stated you could just have a problem with a cap in your sub amp which would not be that hard to fix. If it only makes the noise it in that room, on that one AC circuit, on that one stereo, it must be something else. Maybe the ground for that whole circuit is not good. Do some eliminating of possibilities (different sub cable, or different room/AC circuit, etc).
Nice screen by the way
