Is this affected by the soundstage of the headphones used?
I might be interested in this for my on the go setup, but with the soundstage of the M50x (I love them anyway) it'd seem that they wouldn't pick up the nuances the DSP brings. Am I wrong?
(I don't have the time to throughly test it right now)
The headphones, DAC, and amp will affect the sound, but it's no different than the way your rig affects the sound in general, without Out Of Your Head.
I have found that just about any headphones will give you the "out of head" imaging, even Apple earpods. Of course, higher end systems will be able to reproduce more of the subtleties of the different speaker presets, but in general, any headphones will work.
So I usually tell people if you like the sound of your listening system, then you should like the sound of your system with Out Of Your Head.
The best thing is to try it and see for yourself. If you don't have time to install the trial of Out Of Your Head and test it, you can always just listen to our pre-rendered demo files on our website. No need to install anything. Just use any web browser and listen with your headphone rig. (Go to our website and click on the "online demo" icon on the top.)