It also appears the distortion I heard earlier was my Pioneer because I no longer hear it with the ADA-1000. I guess the Pioneer was just crying uncle.
I had the same experience when I inserted an Adcom ~250WPC amp between my HK 3270 receiver and M60ti's. It was like listening to completely different speakers at medium to high volumes.
I was surprised, although I should have known better than that.
Note to self... you have an ADA1500-4 that you won't be trading in as part of the upgrade to active LFR1100's... open the damn thing up and get it working.