Help - I've Got the Dreaded Transformer Growl....

I'm on week 3 with my new office amplifier - Hegel H590 integrated amplifier driving KEF Reference 1's. Absolutely killer thus far. Dynamic, powerful, detailed, smooth and dead quiet at the speaker. One problem - the amp sometimes produces a buzz/hum at the amplifier. It's typically dead quiet during the evening/weekends but buzzes during the day. The Hegel is dead silent at the dealer so he’s telling me that I either have DC on the line or excessive harmonic distortion on the power line. The dealer says that it’s time to go for a power conditioner.

I’m considering the following power conditioners:

1. Audioquest Niagra
2. Shunyata Hydra or Denali
3. Torus RM 20
4. PS Audio P15 or P20

Does anyone have experience with transformer buzzing caused by DC on the line and did the power conditioner properly address the issue? Also wondering if I should first try the Emotiva CMX-2 AC line filter with DC offset eliminator. A very cheap option at $129. Anyone tried one and did it work and/or degrade your system sound?

Thanks for your help!Ken