Adding sub question

Big difference. The Marantz is a full-blown MC processor which includes Audyssey EQ. Perhaps overkill for you.

The Parasound is more appropriate. You can put a pair of "Y"connectors at the output of the Classe, sending both channels to the ARC and the other pair of channels to the Parasound for its crossover. However, you do not get any EQ for the subs this way.

Let me suggest another alternative: Use the "Y" connectors as above but get an DSPeaker Anti-Mode 2.0 Dual Core digital room equalizer ($1099) which will give you both a crossover and a good EQ for the subs.

I am sorry that I misread your original where you said that you wanted to "keep the full range signal from my main speakers." I read "to my main speakers."

So, the use of a dedicated sub crossover would be what you want and the P2100 would do that, albeit without the valuable EQ.

There used to be good dedicated sub crossovers on the market but they have disappeared. If you can find an NHT somewhere, they were great and cheap enough to let you add an AntiMode 8033 for EQ. I also recommend adding the 8033 to the P2100, if you can.

I continue to be surprised that people with issues of bass response (or other major sonic matters) look at their components through the other end of the telescope. The components that most affect sound are the room and the speakers (and their relationship). Cables? Merely the crust of the icing.

Bo1972 asked: "Is there a system like Audessey Pro what is capable of adapthing 2 sub's togheter in stereo mode?"
I am not sure you mean "together" because Audyssey (in any flavor) will EQ the subs together. AFAIK, only the stand-alone Audyssey Subwoofer Equalizer offers the ability to EQ 2 separate stereo subs. So, will Trinnov and so will DSpeaker 2.0.

AFAIK, AudysseyPro, used with a AVR or prepro, will not accommodate stereo (separate) subwoofer EQ. (It will set individual delays and levels for two subs.)

What hardware are you using it with?