Update: both drivers on my HE-400 now work, though I have no idea what caused the intermittent lack of sound and channel imbalance. Possibly the cable connection?
In any case, I changed over to the velour pads after reading some posts about them. I'm not sure about any differences since I spent all of 2 minutes last night with the pleather pads, but the HE-400 is sounding pretty good. Potentially promising enough to spend a lot more time with them. They're already proving to be effective for more than just bluegrass and ambient electronica, which is more than I can say for my previous HD800 and Qualia 010. And the belly drums on Massive Attack's "Inertia Creeps" somehow went from terribly disappointing to surprisingly awesome. Although that's probably a result of it running on my CD player and properly amped, as opposed to directly from my computer.
Initial impressions are definitely favorable enough to possibly merit a future mini-review, though I can't say my impressions will stay the same as they are now....
Edited by Asr - 12/1/12 at 11:05pm