Lifting ground my only option so far?

Hi. Just this week I received my ATC SCM150ASL pro active speakers. They sound incredible. Thanks to Phil for a great deal on these used but tremendous speakers.

OK, so I had been using some VMPS RM/X's and had driven them with an old Krell KSA-100 amp. I'd always had the Krell plugged either plugged into the wall directly or first into a PS Audio ultimate outlet, then the wall. In either case I'd used a good audiphile-level power cord (bright yellow male receptacle but don't know the brand), but it was two-prong. Any three-prong pc would induce a buzz (not ground loop hum, had that a couple of times, solved it and know that it takes on a 60hz deep hum). I always assumed the buzz was coming from either the Krell directly or some faulty cable in my spaghetti-like HT system. But a two-prong ac cord always fixed it so I never looked further (would try Krell with grounded 3-prong whenever I added new gear, etc but would always revert back cuz of buzz). I know it's not the safest (although not really sure why) but it fixed the problem and I lived with it for many years.

This week the ATC's show up. (Note: The system today is much simpler, no spaghetti, everything is very accessible, and supposedly clean) The ATC's require preamp cabling with an XLR connector; my Modwright pre is unbalanced. While waiting for my custom Audio Art rca-xlr cables I found a pair of RCA-to-XLR adapters so I went that route out of impatience. I plugged both active speakers into the wall with either VH Flavor or Signal Cable Magic Cable power cords (3 prong). Buzz!!! Now the ATC folks, as well as some forum discussions, say that the buzz could be caused by the unbalanced/balanced cable, and that I might need to unhook the screen at one end (I don't know what this means let alone be able to do it). However, I'm still assuming the buzz is the same one left over from the Krell example (obviously it's not the krell...it's no longer in the system). So I put my bright yellow 2 pronger on one speaker, and a cheater plug on the other and voila, the buzz is gone and the music is incredible. New Audio Art cable arrive today. Installed it. Same problem, same solution.

Why write all this nonsense? Because ATC tells me I shouldn't lift the ground of their speaker/amps. I don't know how to unground the interconnects, and feel that the gremlin isn't them anyway cuz this beast has been around for years locked away in 2 prong-ville. I tried unplugging every combination of source, preamp, cable box, etc. I disconnected the cable tv, I tried the amps in other outlets, I disconencted the sub (even though it's not currently in the signal path anyway), everything......buzz is still there in 3 -prong land. Could it be my outlets? The line that the amps use has a four-gang on the front wall and a duplex on the side wall. One speaker/amp uses the side wall, one uses the front...and the front 4-way seems a bit loose in the wall...pushed back slightly from the wall itself. Could that be something?

Thanks for any help....
Ted