Well I've had these for a little over a week now. They are amazing!
I wasn't super impressed with the bass at first, but I will admit that they have really come into their own now. I fixed a connection issue with my FiiO E9 and the power it puts out to the HE-400's is pretty damn awesome. Though less power, my percieved audio quality overall and seperation is better from my Denon AVR-1613 vs. the E9's brute force amping.
Beyond that, removing the foam ring on the pleather pads works great for comfort...I may do the beyer headband pad addition soon. I am curious on earpads...I was thinking about Alpha pads, but can't seem to find too much on them. I may try my D2000 pads eventually too seeing as they're so amazingly comfortable. But I am interested in the Jerg pads. That is in the future, atm I am pretty content overall...they sound so good with all of my music I'm glad I took the recommendations in a previous thread I made on a different forum seriously..and the price, $319 shipped was the tipping point between these and some Mad Dogs. So far, very very very happy I went with these even if they're open-back and that limits my use of them in a full house of kids and women.
I am reading through this thread, but there's so many pages to go through...I'm hoping to read more about different pads like the ones I listed to see what will work best for me. I want to keep as much bass or improve on it as possible. I appreciate these phones because to my ears there's soooo much more detail and openness and the bass more surrounds the sound than interrupts it nor does it seem to muddy anything up that I've noticed! Awesomeness!