Worth upgrading from Rotel RC-1572 to the new RC-1572MKII ?

The New ones are ROON certified.  Might be worth it just to try out that.  But also has a bunch of other refinements. 

Its basically like a big library music interface to you existing service.  If you enjoy music discovery its the best.  If you just want to queue up and album and hit play its not worth it.   Cost you some $ to set up as well.

The Nano is a $300 unit?  I can only the imagine the Texas Instruments DAC in the 1590 is orders of magnitude better.  With a nice digital cable you could see some real SQ improvement in streaming. According to the review I glanced at some of the design and less costly parts have trickled down from the Michi line as well.  1590 has dual transformers I believe which would also be a nice bump. 

My Rotel RC-1572 carries the AKM DAC. The new MKII version has the TI DAC

Its the implementation of the DACs capabilities that really matters. You would think a DAC in a pre amp that cost several times as much as the entire Nano to have put the work into maximizing capabilities. Have you compared the SQ between the Nano DAC and your existing Rotel?