A few specific pointers, a) you should be running the cmc6's into the microphone inputs (not line inputs) of the mixpre -- the mixpre should have plenty of headroom to take the cmc6's signal and the attenuators, which drop the "power" of the mic's signal should be TOTALLY unnecessary. Taking these steps should help clean up your sound considerably. Of course, your mixpre should be feeding your m1 through its LINE (not microphone) input, and you should set the gain from the mixpre so you're getting good levels with the m1's volume knob set at around 7-8 (out of 10, with 10 being full gain)
Next, you should probably start experimenting with microphone configuration -- when I ran mk4s, I had great luck using the ortf configuration -- definitely a good place to start, configuration-wise. Finally, look into mic placement (i.e. where to set up to get the best sound) -- once you've got your system set up properly, this is the single most important factor in getting a setup to run properly