If you are using Nx and Sonarworks together make sure you feed the signal in to Nx first, then that output in to Sonarworks. If you do it the other way around it could mess up the sound.
 
Also make sure you take both out of the plugin chain before you bounce.

I've been using them in that order (makes sense), and they're the only FX in the Master Bus bin.  Simply have to remember to turn off the bin before exporting.  Haven't screwed that up yet, but it's early days.

I think it's pretty good although I'm not sure if I like it more than the VRM Box, which for me fell out of use when I switched to an RME Babyface with no optical output. I would say Sonarworks is more important but that it's still very useful. There are commonly held reasons why mixing on headphones is not ideal, and NX seems to fix them. In fact I'd probably say that mixing through Sonarworks and NX on headphones is a lot better than mixing through monitors in an untreated room. 
 
NX definitely seems to help with ear fatigue as well. I find it's more comfortable to listen to music on headphones with it switched on - you don't have that "closed in" feeling. Although I do tend to bring down the ambiance level from the default slightly. It's well worth doing the head measurements properly as well. 

sharke
I think it's pretty good although I'm not sure if I like it more than the VRM Box, which for me fell out of use when I switched to an RME Babyface with no optical output. I would say Sonarworks is more important but that it's still very useful. There are commonly held reasons why mixing on headphones is not ideal, and NX seems to fix them. In fact I'd probably say that mixing through Sonarworks and NX on headphones is a lot better than mixing through monitors in an untreated room. 
 
NX definitely seems to help with ear fatigue as well. I find it's more comfortable to listen to music on headphones with it switched on - you don't have that "closed in" feeling. Although I do tend to bring down the ambiance level from the default slightly. It's well worth doing the head measurements properly as well. 

The Babyface has optical:
dialog.
I haven't seen the adapter to convert the adat out to spdif though.
 
Rocky

So there's been a new and very disappointing turn of events.
I made some rough mixes of songs I'm working on, and took them over to the studio where I'm going to have them mixed.  MY GOD, they sound awful.  The bottom end was boomy and overpowering, the high end disappeared, and instruments that were dominant were EQ'd into the background.  I was actually embarrassed by the product I'd brought in!
 
I KNOW this studio sounds good, the culprit has to be the mix on my DAW.
 
These demos were mixed with my Beyerdynamic 990Pro headphones, and Sonarworks was on the Master Bus with the corresponding "headphone file" to compensate for BD's "flavour."
 
 
* and yes, I did remember to remove the Soundworks software from the bin before exporting. 
 

Wow!!
So, the demo's sound good on the H-phones with the software enabled (at home), but not in the studio? Something's not quite right here....

What does the output look like on a spectrograph and how does the sound compare to a reference track?
That may give you a clue.

I got NX some days ago when Waves gave that $20 coupon and I was planning to get Sonarworks until I saw that Toneboosters released a much cheaper similar plugin last year (Morphit). Maybe you can give it a try.

Another followup:  this one was a "Keyboard/Chair interface error."
I had a  compressor on the Master ProChannel (i never use that, must have done it accidentally and/or forgotten) that "adjusted" the frequencies.  
 
 
PS.  Thanks for offering to help!

Using both , i would not use nx before sonarworks cause when sonarworks created the calibration files they didn t used nx or something else , just straight from your headphone , so i would do it sonarwork , then nx .... the key in all cases to really aprecciate dynamic ranges and spacialisation is to monitor at low volume in headphones ...