Sibilance

A lot has to do with the quality of the accuracy ,or lack of your digital quality , I have had many dacs from $800 to$10 k 
and it is a profound difference in musicality .
Sibilance can be from from jitter or digit er errors . I purchased a Bricasti dac with streamer module and it’s a win win more direct 
and two less cables . Also a high quality Ethernet cable to streamer is the most influential ,and second from modem to router.
Uptone audio Ether regen is one brand that cleans the dirty signals that travel from the street to your home ,for the money a excellent buy IMO, and BTW the reference Ethernet cable from Jcat audio
is a bit $$ pricy but sonically superior and I have had many up to $1500.

I noted the comment blaming it on speaker response in the 3 kHz area. That's often near the crossover to tweeters. And crossovers can be crazy. A speaker can be flat in the crossover region but if the transfer function(shape of the roll offs at crossover) are not 'nice' then there can be ringing in that area which will sound sibilant even though the measure response is flat there.

Vibration was mentioned earlier. Are your components isolated from your rack/furniture? Are you using any footers to decouple or drain vibration from the components?

My system suffered from harsh highs on many digital tracks, CDs and streaming. It took me awhile to find that the DAC was vibrating on it's shelf. I was using aftermarket footers but they weren't good enough to stop the vibration of the DAC. 

I noticed the same harshness on my system ( $ 12,000) until the Ares 2 DAC was introduced into the mix. A good quality R2R DAC would help you and really open up the soundstage on recordings from Pink Floyd.

If you're using the Node2i's internal Dac, then I agree with buddyboy. Adding a standalone DAC will improve SQ in every way. A R2R multibit has a more forgiving presentation.