Okay, so I think with a piece as nice as the Marantz, you will be best served with something at another level than the old DR120's for sure. This is one of those situations where the old tech of those speakers just can't keep up with the signal from that Marantz. For speakers you could do something somewhat vintage like ADS, or go new where there are tons of options and you just gotta balance budget with, size, access etc. Could be fun. With the PM8004, do you have the Source Direct engaged to bypass the tone controls? Also, did you try another source like a CD player of turntable yet with it to see if the phone signal is adding fuel to the fire? Update: Looks like above while I was typing you mentioned using a CD player.