OP -- I would start with a lower cost balanced cable and, as others have suggested, try borrowing something expensive to compare. But I would only do that comparison after living with the Atmasphere amps for a while. Also highly recommend prioritizing budget for a preamp before pricey cables. That's going to make a much bigger difference in the sound quality you hear. I've tried the streamer (with volume attenuation) into the DAC directly into the amp and didn't love the sound at all. If you had something like a Lumin U2, maybe that would sound good with Leedh processing but I think you're giving up a lot doing it through Bluesound Node. Sounds like you're getting a Burson to try -- haven't heard it but better than no preamp.
I'm really curious about your bake-off between Decware Zen Triode and Atmasphere digital monoblocks with your Tektons. I can't imagine they'll sound anything alike and seems like an odd comparison, but very interested in the results.
Have fun!