Do Streamer only devices really impact sound quality?

Only a boob would believe that.

I did write that too fast, and I'm sorry but let's be nice to those just starting to learn.

Even the best asynchronous DAC's can be impacted by really bad streams/streamers, especially streaming radio.

For the most part, a good low noise clock on a DAC with asynch USB is pretty awesome but they can't do magic, and if things upstream get bad enough, including if a digital ground loop occurs the DAC could be subject to less than ideal performance. 

Another reason I chose the N200, I can use either it's USB or Coax.    I think my DAC sounds better via Coax .  I think the clock in the Aurender is better than in my DAC,  this would explain why I think the Coax connection sounds better.   My other DAC uses it's internal clock whether you use USB, Coax, or Tos so I can't make any comparisons.  Maybe down the road I'll have a DAC that sounds better via USB, who knows  ut it's good to have both outputs.   I run the USB out of the N200 to my headphone rig , a RME adi2 .   

For many devices recently on the market, the streamer is integrated with a DAC and possibly preamp capabilities (volume control, source selection, or both). So chances are, you won't be hearing the "streamer itself" in isolation from one or more of those other functions. Furthermore, streamer A and streamer B may be delivering different combinations of software effects (DSP) or source content, which all color the output. FWIW, Stereophile does not have a separate category for "streamers" in its annual list of recommended components. They have a "digital processors" category, which mostly covers DACs (many of which have integrated streaming or preamp capabilities, equalization, DSP, etc.) 

So, while In theory "everything is important", I doubt that anyone here has done controlled, volume-leveled A-B comparisons among multiple streamers in a way that focuses solely on the streaming functions, per se, of all the compared devices.  I'd venture to say that the impact on SQ of the streaming capability, per se, probably is somewhere between negligible and unobservable compared to the impact of the DAC and especially the preamp effects.  But I don't really know for sure, and would welcome anyone to point out a good comparison of multiple streamers, one based on some credible combination of metrics and expert observation. 

@tk21 I know it can be tough to accept that streamers make a big difference, and I applaud you for at least keeping your mind open as opposed to many here who just close their minds based on their beliefs rather than just listening.  Most experienced listeners here observe significant differences between streamers and that they’re at least as important as the DAC they feed.  Darko did a head-to-head comparison of several streamers a while back and found significant differences in sound quality so might be informative searching that review out.  My advice: Trust your own ears and come to your own conclusions because that’s really all that matters.  FWIW…

I did a quick search for Darko's streamer reviews.  Not sure I found the one @soix cited.  Anyway, Darko's highest praise seems to go to the Logitech Squeezebox Touch.  You can get one of those on eBay for less than $200 (US).  I wonder if anyone here has heard a significant sound quality improvement in going from the SBT to, say, the Auralic Aries G2.1 ($5699).  Not necessarily 30X better ... but at least noticeable to the average listener.