Should I use the dac in my node2i or the one in a marantz av7705?

If you're using the Marantz for two channel listening, it's probably not going to make a big difference.  That's not exactly an audiophile pre-amp.  However, as others have said, try it and see. 

Most two channel enthusiasts would not use a home theater processor for two critical two channel listening, so it's highly unlikely you'll find anyone that has tried both.  I had a couple of Node 2 units for a while, and have a Marantz AV7704, but the thought never occurred to me to compare the DAC in the Marantz to the DAC in the Node 2 or to any of my other DACs.  

I'm not trying to put down your system.  I used a home theater system for listening to music for many years, but reached a point where I realized that I needed to move beyond that to achieve better sound quality.  It sounds like you are headed in that direction.  Consider getting a two channel preamp with a home theater bypass function if you're looking for a way to get the best sound out of your system. 

I have the Node 2i. Mostly listen with the RCA output going into a Marantz PM-10 amp. I also have it connected to a Marantz SA-10 by a digital coax cable. The sound is pretty similar. The SA-10 DAC does seem to have a bit more detail and space. 

I listen a lot to Radio Paradise, which uses MQA encoding. Probably losing that going through the SA-10. So your results might be different, depending on the details.

Thanks for all of the great advice! I have a Parasound Classic PRE 200 that might have a ’by-pass’ function. I think I will try to figure that out as a next step.

It's currently connected to a pair of marantz ma500 amplifiers in a bookshelf system.

The next question which DAC might be ’better’? the Node2i or the one in the PRE 200? I realize that it will be ’the one that sounds better to me’, just seeking out the learned opinions of this site.

Honestly, I have a bunch of gear, new and old, in a few mixed systems.  Any suggestions of a 'best' combo for a two channel system is appreciated.

Speakers:  Magnepan 1.7i; B&W607, Linn Tukan

Amplifiers: Proceed HPA2; HPA3; Marantz MA500; MA700; Parasound A21

Preamps/Processors: Marantz AV7705; Parasound New Classic PRE200, Parasound zPRE3, Proceed PRE (not hooked-up)

Digital Sources: Rotel RCD1570; Node2i(x3); CAL Tercet MK-iv

Thanks!

IMHO, the DAC is a critical piece of kit on the front end and I prefer a stand alone option with its own power supply and a pleasing analog stage.   

Stream --> DAC --> Preamp(tube) --> Amp --> Magnepan 

A recipe for success.  I find that the "dac is just a dac" crowd have it wrong. 

Thanks for all of your input.  I will continue to experiment with various combinations.  I may look for an affordable standalone DAC for comparison.  Thanks again all!