Requesting Guidance/Advice - Xonar Xense + DT 880 Pro 250Ohm Listening Test Settings

[jpongin]

Hi, I just ordered the Beyerdynamics DT 880 Pro 250ohm, and it's going to plug right into the Xonar Xense.
 
After break-in / burn-in and such, what is the proper way to test the subjective listening quality on the Xonar Xense for the purpose of listening to music (320Kbps lossy from Spotify)?
 
With my bundled PC-350s, I had to:

1. Modify EQ
2. Set Audio Channel to 2 Channels
3. Analog out to Headphones
4. Gain to the specialized PC-350
5. SPDIF out to PCM - no virtualization
6. FlexBass to High
7. Volume to 80%
8. Effect to Carpeted Hallway (Medium sound stage)

 
From what I read, it seems as though I should select the "HiFi" preset to test out the DT880s.. which essentially flattens the EQ and doesn't apply any virtualization.  I plan on setting the gain setting to the lowest setting, and raise as needed.
 
So after that, I have the following questions:

1. What is the best environment setting for the DT880s?
2. Should I disable flex bass?  I heard these cans already provide plenty of it.
3. Do I need to get my ears acquired to the flat EQ?  Or will EQ'ing the DT880s hurt its intended performance?

 
I know I should set it to whichever sounds "good" to me, but I'm trying to up my taste for what's considered HiFi... trying to get a sense for what good texture, richness, effortless-ness, extension, tonality, and transparency are like.
 
Thanks in advance.