This is just my opinion, but a "receiver" that uses a Class D ICE amplifier circuit can't be too good. I would try to borrow a seperate 2 channel power amplifier and see how it sounds.
4 responses Add your response
I would try an amp that could drive 4 ohms also.The speakers are 5 ohm nominal,with a dip down to 1.6 ohms if I'm reading the correct manual.Your receiver is rated down to 6 ohms.I think trying an amp is a good idea if you could get your hands on one.Links for both.[http://www.martinlogan.com/pdf/manuals/manual_source.pdf]Page 25 on back of receiver.[http://www.pioneerelectronics.com/StaticFiles/Manuals/Home/SC-25_OperatingInstructions0421.pdf]
One other possibility that may be causing a problem is the automatic equalizer,if your using it.It may be trying to compensate for a slight room problem,and over/under driving
your ML's at a certain frequency.I've read where some reviewers state that they had to fine tune it themselves. I don't have enough hands on with them,to give any advice for them.
Thanks for the advice guys, I borrowed my buddy's Marantz integrated and it knocked the pioneer out of the park. The issue with muddied mids was resolved simply by switching amps. I had hoped my existing receiver would be sufficient to push my newer speakers but it seems a dedicated 2 channel amp was a far superior option. I appreciate your input.