Where is the weakest link?

You’re running a $5500 stereo DAC into a prepro. Cables are the least of your worries. Get a good stereo preamp worthy of that DAC and run the Chord along with the front L/R pre outs from the NAD into the stereo preamp so the NAD is out of the 2-channel signal path, then you can worry about wires IMO. A good stereo preamp will absolutely stomp the NAD for 2-channel performance, so to answer your question the NAD is your weakest link relative to the rest of your system. 

What is it that you are trying to improve upon? You do not indicate what your perceived area of weakness is...what is it that you are hearing or not hearing? That may help point in the right direction. Just remember, there is nothing that is perfect. 

Focus i have is cables, i do have a cheap stereo tube preamp that i plan to insert, a schiit freya that i want to replace. I will run chord dac into a tube preamp eventually. Am testing the nad’s stereo playing expertise.  I dont like using a tube preamp in a home theatre system as no one has created a nice high end stereo tube fit that is convenient and is a true ht bypass.

great comments herein, thanks.

no one has created a nice high end stereo tube fit that is convenient and is a true ht bypass.

I believe Rogue, VAC, and Backert make tube pres that may work in bypass mode without tubes glowing so might be worth checking out. 

Anyway, in my system I get the biggest impact from interconnects closer to the source.  I’d start with an Optical Rendu from router to streamer, then I’d replace the Monster with an Acoustic Zen Silver Reference interconnect (balanced if possible) as it’ll preserve all the detail/dimensionality of your DAC without adding etch or bleaching tonality.  I think those two changes will make very meaningful improvements to start.  Hope this helps, and best of luck in your search.