The right amp for my system

if the pioneer isnt up to the task, then the marantz probably wont do it either. You need to step it up to something in the realm of an Anthem at 200wpc. The Pioneer is a nice unit but when you put that much in one box, it does have it limitations as you've seen.

I have a 130w Pioneer Elite. I drive the center and rears with the Pioneer, thus preserving all the functionality of the receiver, including driving ceiling speakers in other rooms with channels 6 & 7. I inserted a Wyred for sound STI 500 integrated with a home theater bypass for 2 channel. Before that, I used the Pioneer as a pre-amp and ran it through a Rotel 1095 for 5 channel amp. Sounded great, and was less complicated for the wife and kids to use for movies. You could probably talk me into selling the 1095 if your interested.

Martin Logans are tough to drive, with a wild impedance curve. No receiver is going to drive them properly.

You are likely looking at a good 150 - 200wpc dedicated power amp with lots of current. You could use the Pioneer as a pre, but once you've invested in the power, you will likely find the pre lacking.

If you like the speakers, save up a bit and go for a decent pre/pro, power combo.

Previous comments are correct. If I understand correctly this is a 3 channel theatre system. Might consider the Odyssey HT-3 three channel which will provide enough current as suggested AND proper damping factor to control the panels which is oft overlooked.