Just to clarify:
The Asus cards have 3 different gain settings: 0-64, 64-300 and 300-600 that are combined with system volume control. I'm assuming that EVGA's Nu has a 0-600(gain)/0-100(volume) by using a master volume as well as the speaker/headphone volume?
So far no problems driving my beyerdynamic t1 gen2 blacks. Master volume maxed, headphone 50-75 depending on the source.
The only feature I've used is the Noise reduction, 100%. There seemed to be some static on some tracks that I don't remember being there when using the STX.
I played a little Diablo 3 using the Nu. When you get into heavy melee the Nu does a better job controlling the chaos of the moment, basically it stages the fight sounds better than the STX. I'll have to double-check that against the Denon 2000s which I had been using as my gaming cans due to better sound isolation/closed back. The t1s are semi closed with velour pads instead of the Denon pleather ones.
Will update as I get into it....
Did some more listening as well as popped in a Burson V6 Vivid to the Headphone Op Amp socket to match the one installed on the STX. The STX plays louder for lower volume settings, I have to assume due to the dedicated gain settings. Not a big deal, but certainly noticeable.
Did some more comparisons with gaming, the difference in sound stage I reported on earlier seems to be more headphone dependent. The Denons seem to be more mid frequency intensive than the Beyerdynamic. Its not necessarily a Nu/STX thing, not that I can tell. I adjusted the equalizer in the NU software in the 500/1000 frequency range to make the mid frequencies pop a little more on the T1s.
On the software side:
Asus' dated Xonar Sound Control has the upper hand, probably because I've been using it for close to a decade... Seriously dated, but everything is right there easy to configure and dabble with. Plus it has a graphic equalizer. I would like to see the saved equalizer profiles as a drop down menu then they can replace the spider web selector with a graphic equalizer.
I like the full length shielding, unfortunately I will have to drill it to accommodate the Burson Op Amps. Really nitpicking here; but I wish there was a little more spacing around the swappable Op Amps. I had to uncomfortably bend the CAPS to get the Bursons fully seated. Going with any other Op Amp should not be an issue.
Overall I plan on keeping the NU in the system and I'll put the STX out to pasture.
Day 4 update:
The static I thought was present from the card seems not to be something coming from the card, haven't been able to reproduce it.
I modded the cover to accomodate the Burson V6 vivid op amps. Drilled holes in the location of the 2 op amps. Added bonus: now I can roll op amps without having to take the card apart. I also modded the plastic covers of the op amps to accomodate the caps positioned around them... piece of mind.
So far everything is pretty good.
Annoyances:
The software doesn't seem to want to start minimized when the computer turns on. Not sure if it's the code or if it is Kasperky preventing it. The "start minimized" box is definitely checked. I have to open the software and then I have to "show" from the toolbar.
The 2 volume controls. I prefer to have the master volume at 100 and adjust the speaker/headphone volume as necessary, which requires you to have the software up. May try to program some spare keys to adjust the headphone/speaker volume/gain.
Annoyances that are not the cards fault: Beyerdynamic sibilance is real (female and Ed Sheeran vocals). After 3-4 days of break in the brain piercing highs reared their ugly heads. Had to equalize them down to enjoy the sound again (-3 on 4k, -8 on 8k and -3 on 16k), unfortunately that also ruins some of the detail/nuances of the instruments. "Sound color" options do not seem to effect it.