We used the Sennheiser HD 280/HD 650, Beyerdynamic DT 100, Beyerdynamic 770 and the PROline 650s to test VRM with, though during development the concept was tested on a wide variety of headphones of different designs (e.g. open and closed) and of varying cost and quality.
Obviously the better the headphones in terms of frequency response, the more the individual speaker's qualities will be discernible. However, the VRM system was not designed with one specific model of headphones in mind.
When considering headphone impedance, the general principle is that higher impedance headphones typically have a flatter frequency response, however they require more power from the headphone amplifier to provide the same output level as headphones with a lower impedance. Having said this, the VRM Box's headphone amplifier should be powerful enough to drive higher impedance headphones at a high enough level for most purposes.