Ground Lift on PC, but Grounding Chassis to Outlet

I know we've been through the issue of 'ground lifting' countless times here, and I don't want to start a flame war over safety vs. sonics; until recently, I was able to establish quietude with everything plugged in, as it should be. For some reason, after getting my ML2 amps back from Vlad, I have a ground loop. Here's how the AC is currently configured for the system: 3 dedicated lines to a separate subpanel, all done per code; there is obviously a differential between the outlets, which are in different places in the room. The front end electronics (Steelhead/Lamm L2 Linestage) get plugged straight into one quad outlet (dedicated line 1); the TT motors into dedicated line 2; the ML2 amps and the Avantgarde powered woofers get plugged into strategically located quad outlets on the other side of the room, dedicated line 3. I managed to eliminate the ground loop with one of those Granite Audio Ground Zero boxes, after much experimentation and flipping of switches and rearrangement of plugs, but all PCs were fully plugged in, with their 3 connectors making contact into the wall sockets for every component. (FWIW, what was additionally 'grounded' thru the Ground Zero was the Lamm line stage and the subwoofer amps on different 'planes' per the Ground Zero set-up and switching 'impedences' between the line stage and subwoofer amps made the grounding noise dissappear; this worked fine).
Now, with the ML2s back from the Vlad, this arrangement doesn't seem to work. (Keep in mind at this point, no lifting of grounds from any of the PCs). So, I tried connecting the ML2s to the Ground Zero on one 'plane' with the Lamm Line stage on another- after countless switching combinations, no joy- still some hum.
If I lift the ground, using the dreaded 'cheater plug', from the Lamm line stage, total, utter, blissful quiet. No hum.
So, if you've followed this so far (thank-you), here's the Question: even if I lift the ground from the Lamm line stage PC (no other component PC grounds are cheated), I then run a ground wire from the Lamm line stage chassis to the Ground Zero device. The Ground Zero is also grounded to the same Quad outlet as the Lamm with its own 3 prong plug-entirely passive- just grounds the Ground Zero, if you will. I then added the Steelhead to the Ground Zero hook-up and can add either the Lamm amps or the Avantgarde powered woofers to the Ground Zero grounding array, with no apparent ill-effects.
My question is, am I actually grounding the Lamm line stage by lifting the ground at its PC, but running a separate ground from its chassis to the wall thru the Ground Zero? And, as related question, do I need to keep any of the other stuff hooked up to the Ground Zero device, since all else is plugged in with 3 pins?
Sorry for the length of this post or its convolutions. And many thanks in advance for helpful replies.