I’ve had a few more days to listen to these, and today I tried driving them with my Total Bithead headphone amp. They sound even better on these, much more full base and clarity, but they also make, as Ramesh noted, the backround hiss of the bithead really obvious. The hiss on the Bithead is a known characteristic, but I guess I didn’t notice it on the higher impedance headphones I had them plugged into. The 5Pro’s are only 16Ω so even really small things in the signal come through crystal clear. Oh well, I guess maybe I’ll have to find something else.