I have an extensive library of music - over 10k tracks - a lot of DSD / High Resolution PCM files and CD quality FLAC files that I've painstakingly converted myself. I was looking for something to upgrade my on-board sound that is based on the Realtek ALC1220 codec in my PC build (MSI x470 Gaming M7 AC Motherboard). The on-board was sufficient for my "gaming" in 7.1 with analog 7.1 Razer headphones.
Lately though I've been using my wonderful external iFi xDSD USB DAC with Sennheiser HD660s headphones for pretty much everything. I use headphones 99% of the time on my computer - for gaming or work or music and I switched back to stereo from 7.1. I use Audirvana for PC to play music (absolutely fantastic software).
 
When I was looking for an updated sound card I had only very few and limited options:
- SB X-FI Platinum HD old with meh drivers
- Asus STXII (this one does not work with x470 based motherboards)
- Asus Strix Raid DLX - I've tried this one but was very disappointed with the drivers (no bass management implementation for 7.1) and really bad hum and interference whenthe video card kicked in that was the dealbreaker.
- SB AE-5 - I was just not impressed with the features. And Creative drivers can be finicky
 
so when the EVGA NuAudio was announced I got very excited - native DSD support, 32bit 384k, swappable op-amps, analog volume for DSD, AudioNote involvement, ASIO support.. all good stuff
...and the card did not disappoint. I am writing this after a week of testing and I absolutely love it. I must confess though - I did upgrade the pre-installed headphone op-amp with NJR Muses02 op-amp. AND OH BOY did the card wake up!!! Everything just opened up on my Sennheiser HD660s cans. I will even say that it sounds better than my beloved iFi xDSD DAC. It absolutely blows away my Pioneer XDP-30R High Resolution DAP.
I can't even tell how many times I've listened to my go-to reference DSD tracks like The Man's Too Strong (Dire Straits), some Norah Jones, Steely Dan's AJA, MJ's Thriller, Counting Crows and bunch of classical stuff - all in DSD. The EVGA NuAudio (with Muses02) just hits it right out of the park every time.
 
So as far as the audio goes the card is just wonderful.
But as with any new product there are some issues - mostly with the drivers. The drivers are very basic - which is fine by me. But some users had issues installing them. I did not run into these runtime issues. I did have some random crashes of the software that seem to have stopped with the latest driver version (0.1.1.0) and I am confident that all of these problems can be fixed with more mature drivers.
 
I would love though some improvements and added features to the drivers:
- It would be nice to have global auto-mute in the drivers during PCM to DSD mode switch. I do get a click sound when switching playback from PCM to DSD files. There is no
   click when switching back from DSD to PCM. I am using Audirvana and I am not sure if this is an issue with the card or the player software but it would be nice to have
   enforced mute during the mode/rate switch.
- Because I do use headphones most of the time I keep the master volume at 100% and adjust the volume with the separate headphone analog volume. It would be really nice
   if you could assign the analog headphone volume as "master" so this way the volume could be controlled with a keyboard knob instead of going into the NuAudio software.
- It would be nice if the engineers could add MQA support - if at all possible. I know that MQA as a format can be controversial in the audiophile community but MQA support
   would be nice for streaming services like Tidal etc.
 
I still have to run the card thru it's paces in gaming. I've played some stuff and the card performed really well. Shenua sounded great
 
So to close this - the card is absolutely wonderful - even with the stock op-amps. And it wakes up into greatness with something like NJR Muses02 or Burson op-amps.
It's definitely not for everyone. Casual gamers will probably not appreciate the card for what it can do. But if you would like to clean up some clutter on your desk and at the same time get a fantastic sound card then look no further than EVGA NuAudio.

Should i install Muses02 instead of both stock OP-AMPS or just one for the headphone output will be alright?
Also, i've noticed you have the same headphone. HD 660S. And this one sounds a bit dull for my liking. How whould you describe the sound difference between stock OP-AMPS and Muses02? Will the sound become brighter and clearer?
Also, is there a specific way to install Muses02? I mean it has 8 pins. Does it matter which side it's facing? Do i need soldering? Thank you! 
 

I did, but i'm dumb in everyting related to electronics :D
So the question is, if i'll just install 2xMuses02 instead of line out and headphone out stock OP-AMPS... Will it work?
Cos i see Muses02 in compatibility list of line out OP-AMPS and can't see it in headphone out list...
Topic starter tho, mentions the headphone out OP-AMP, so i'm a bit lost.

Thank you! Now waiting for topicstarter to answer. Wanna know the difference in sound in comparison to stock OP-AMPS.

SubL0ck
Finally swapped stock OpAmps to Muses02 myself and have to say... Yes, that was absolutely worth it. The card performs so much much better now and sounds in different class, really.
All the mud in the mids gone, sound became cleaner, airy, with awesome stereo separation, much wider soundstage and much much much better, deeper, more fundamental bass. It also sounds much more energetic, powerfull and expressive.
HD660S came to live now with this upgrade. 
Totally recommend!

@SubL0ck
 
Can I ask where you purchased the Muses02?  I tried looking but my usual go to places don't seem to have them or I don't know if I'm getting the correct ones.

SubL0ck
 
Definitely avoid purchasing the opamps somewhere else but official stores.
The risk of buying fake is like 99%.
The stores that are official and safe to buy from:
digikey.com, mouser.com, profusion.com (the one i used).
 

Thank you for the response. I'm definitely going to try that out. I have owned and used the Nu Audio (non-Pro) since it released with my HD660s. I'm curious to see what this "mod" can do. It sounds fairly manageable to switch out and I can always switch back if I'm not satisfied.

Would you recommend this for the Nu Audio Pro? Or only for the regular Nu Audio?