172-155 or SuperUniti?

I can't comment on the 172-155xs, however I delved into the world of hifi last year with my SU + Totem Arro purchase, and couldn't be more pleased. Have since added a PL, and Turntable. The end result is an extremely versatile and excellent sounding hifi setup. My primary source is FLAC streamed via Upnp over ethernet, but my vinyl collection is quickly growing. I also love the Internet radio available directly on the SU, and I've recently plugged my iMac into the SU via digital optical cable. To me the SU offers more versatility than the 172-155xs, but your mileage may vary. The 172 combo is a little less expensive I believe.

I listened to ND5XS/152XS/155XS (before 172 came out) vs SuperUniti and marginally preferred the separates. Slightly faster, leaner and more detailed. Really liked both and it would be a matter of personal preference. SU is a great one box solution.

In the end I've stuck with my Sonos ZP90 as my streaming source and upgraded my amp instead. 

I would go for NAC N172XS.

One of Uniti (I have one), UQute and SU's main features is a variety of options for sourcing.  But having had Uniti for the last 2 years I have realised I actually do not need that much flexibility.  For example, I use the iRadio as the source some 99.9% of time and I have played CDs maybe 20-30 times in total since I bought the unit (!).  So now, I would probably go for the less albeit at better quality.  Chances are the N172's DAC and preamp are better than those from the Uniti range.  And if you ever decide to upgrade your speakers you will have the flexibility to add a quality power amp.

Bobby

Let's not forget that the Superuniti is a 'reference level' one-box solution, so I wouldn't be making assumptions about the quality of the DAC and Pre in relation to N172-XS. I think future needs and space requirements are a valid consideration, but only an audition will tell you what you prefer sound-wise.