My apologies - my comments were directed to djones51 - not at you, the OP. Sorry for the confusion.
I recently went down this same road, thinking the Node 2 was the weak link holding my system back. I went to my local dealer and a/b’d both units connected to chord Dave and gryphon int. What I heard was a VERY minor improvement in the U1.
I bought the U1 mini and SBooster mod at the same time. I had it 48 hours before doing any critical comparisons having both setup to a Schiit Gungnir MB. The Node via digital coax (bnc) and U1 via USB (old printer cable I had lying around). I level matched and then did some a/b comparisons for a few tracks and there was literally no difference. However, I have kept the mini as many say it needs 100 hours to break in and I have a better usb cable on the way to hopefully help bring out the best in it. I do feel like it has gotten better over the past week but I have not tested against the node again since the last time. I will likely have some time this weekend and will do some more testing but if I were to do it again I would have saved the money and traded my 507uxII in for a 509x. I think that would have been a more worthwhile improvement. The node is heavily underrated for what it does.
I gotta say the best improvement I had in my digital source was from adding the EtherRegen. Many say it’s snake oil but it was a clear upgrade in my system.
I also just received the Denafrips Pontus II and will be testing that against the GungnirMB to see if there are any improvements there.