Audioraider, if you swapped the arm wiring at the cartridge clips and the problem moved, its the cartridge.
However now we have 3 cartridges that all seem to have the same problem, so its getting less likely that the cartridge is to blame. I also doubt setup, and I also doubt that moving the 'table will do anything.
Right now I suspect that the problem is very close to the cartridge. It could be that the arm wiring is damaged right be the cartridge clips (although I am struggling with how that would work) but the other thing that is worrying me is that you might have DC at the input of one channel of your preamp, so that any cartridge you put on there gets damaged. The only problem with that idea is that if that were the case, swapping the channels would introduce the 'damage' to the other channel of the cartridge and it seems like that has not happened.
Since there are all dead ends, I suspect that there is a procedural error that is confusing things, like a channel that was swapped with the other but for some reason really was not, even though you were sure it was- some sort of thing that you are convinced of and so you can't see it.
If it were me at this point I would start from square 1:
swap the interconnect cables at the inputs of the amps and see if the problem moves
if no => amps, if yes => preamp
if preamp then swap inputs to the preamp (phono input since CD seems OK).
if problem moves then its the arm
if stays put then its the preamp
If arm, swap channels on the cartridge. if problem moves its the cartridge, if not its the arm.
Now I would do this and take notes, being certain that at each step you *change only one thing*. So this means you can't touch the volume or balance controls. Sorry to lay it out like this, but I can see why you are at the end of your rope...