I have an Aragon 4004 MkII amp, brand new Yamaha Aventage RX-A1040 receiver, with B&W 802 Series 2 speakers. I recently installed the system in a new rack system and am pretty sure there is very subtle yet audible hum/buzz coming from both speakers. It doesn't sound like a ground loop as the noise is coming from the mids and tweets as well as the woofers. I'm only mentioning these components as I believe I have narrowed it down.
Do you have the Aragon amp somehow connected to the Yamaha receiver? If so how?
With just the Yamaha receiver connected to the speakers try connecting a DVD or Bluray player to a set of line inputs on the receiver, nothing else connected to any input or output of the receiver. Have everything else on the rack turned off and unplugged. Check for hum/buzz. Post back your findings.