Guess you'll have to give it all to us, then: FR, CSD, THD, square wave, isolation, the works. Oh, and on every measurement system possible. ;)
Kidding aside, I'm actually most curious about any changes in harmonic distortion. Measurements show that's one of the weaker areas of modded T50RPs (not bad by any means, but not particularly fantastic either). I'm curious how much of that can be changed by the housing/damping and how much is just inherent to the driver itself. I'm sure unit-to-unit variance also plays into this to some extent. FR is most useful in combination with other measurements, particularly CSD and THD, IMO. I'm guessing there will be other types of measurements to regularly accompany and expand on these in the future that will better "represent" a headphone's sound as heard by humans.