I would put my money into a Node + LPS combo, no question. This is one of the best bangs for the buck across all audio. Adding the LPS will reveal much more and at the same time tighter bass. It will take the SQ of the streamer up to that of the multi thousand dollar streamers.
I can't speak to the stability of the USB output, I'm running coax to my DAC. The Node+LPS combo is not below the level of your DAC. I'm running a much more expensive DAC and it sounds very, very good. I would take a look at the Teddy Pardo LPS, I've had zero issues after the conversion. Good luck and cheers.