Agree with all the points made in the posts above. The DAC in the Node 2i is the weak link in your system. So definitely start there.
Having said that, the Node 2i even as a standalone streamer is still going to be the weak link. I recently replaced my Node 2i with a Sonore opticalRendu which made a significant difference in SQ. If you buy it from SmallGreenComputers, they sell it as a bundle that contains everything including the opticalRendu, power supply, fiber optic cable, as well as a media converter to convert ethernet to fiber optic.
Having said that, the Node 2i even as a standalone streamer is still going to be the weak link. I recently replaced my Node 2i with a Sonore opticalRendu which made a significant difference in SQ. If you buy it from SmallGreenComputers, they sell it as a bundle that contains everything including the opticalRendu, power supply, fiber optic cable, as well as a media converter to convert ethernet to fiber optic.