Got Noise?

OK Guys, need your help with this one. Recently I've noticed a fairly high degree of background noise (sounds like a "ffffsss" coming through my system at idle. The noise is only audible when the amp is turned on, not any of the other components. The amp has been tested by the manufacturer and he reports no issues. (Amp is a Modwright KWA150 and I asked Dan to check this for me when he did the "SE" upgrade a month or so ago). The level of noise is audible when I am playing music only at very low volumes, which has been the case over the past 4 months since we now have a baby on board. In fact, it is possible that nothing has changed but the simple fact that before the baby I was listening at higher volumes and did not notice the background noise. On the other hand, it is somewhat intrusive and if there is something going on elsewhere then I'd like to address it. FYI I have a 20 amp dedicated line to my system and have an Environmental Potentials 2050 surge suppressor/noise cancelling device installed on the panel, which I had my electrician confirm has been correctly hooked up. Is it possible that something is happening at the pole where I have a transformer shared by two other neighbors? I can't decide whether this is a new problem that has developed or simply an old problem that I did not know was there until I started listening at much lower levels in the past few months. Tell me, when your system is at idle how much noise do you hear when you put your ear to the drivers? Or from your listening position?