Peachtree Audio 2.0

 Paksiw, did all of that testing, with multiple amps, multiple speaker cables, cd players, etc. happen at the dealer or did it all happen in your home?  Were you and the dealer able to re-create this noise at the dealer on one of his units?

Obviously, any brand can have a quality defect, but I'm thinking that the statistical probability of getting back to back units with the exact same defect is probably pretty slim.  I think cusco69 is barking up the wrong tree with the "cheap parts" and "common issue" claims as well.  

My guess is that there's something else happening, but I'm just not experienced enough with the ways of electricity and power generation to give any tips.  But there are some very smart people on this forum who've dealt with ground hum and RF noise and the like and can probably offer some ideas.   It may not help in this case, since you've already returned them, but the knowledge may be helpful for future situations.