Loss of Sound Quality when both systems are ON

Hello All You Good People

I have come to somewhat of a dissapointment in my setup. I'm hoping it's an easy fix. Over the years i have listened to a good number of amps and speakers. I have come to a personal conclusion on what i like my stereo setup to sound like. I bought two pairs of tube amps, four speakers and run them through a preamp with 2 sets of outputs. When i use each set separately, everything sounds beautiful, bass is full, mids and highs are excellent on each system. But...when i use 2 sets at the same time, the sound coming out from my speakers are dull, almost no bass, lost mids, as if there is not enough power coming to the speakers. I have tried separate electrical circuits, no luck.

HOW CAN I FIX THIS?

This problem is fixed when using amp/preamp's own power, and output 2 (external amps). Both output 1 and 2 are on and they sound great. But as soon as i wire the system so output 1 and 2 are external amps only, the sound they produce is faulty when both outputs are on at the same time.

Here is my system.

McIntosh MA6600 amp/preamp 200w/channel 2sets of outputs
Pair of Cary SLM-100 mono blocks 8ohms 103W Liniar Mode
Pair of Cary SLM-100 mono blocks 8ohms 60W Triode Mode
Pair of Klipsch Chorus II 100W nominal power 8ohms
Pair of Klipsch KG5.2 100W nominal power 8ohms