I have the hd 555, I love em but the bass response lacks slightly. When Ive tried mixing with them before the bottom end sounds in balance there but way too loud on everything else.
The bass response on a lot of the HD series has been a complaint from audiophiles for a while now actually, so you are definitely right about that. Even with my HD 598's I notice it. I'm not an audiophile so I'm not as concerned with all the technicalities of it.
Bass response an balance don't play together well on small speakers. The reason people like the way headphones like beats and such sound is because of a huge boost in the low range that is essentially faking lower frequencies on your headphone speakers. Your best best with headphone is a $50 pair of akgs unless you want to go up to the higher priced sennheisers, but it kind of depends on what you need/are using them for. I think beyerdynamic makes some pretty good headsets as well.
http://www.sweetwater.com/store/detail/K77?adpos=1o8&creative=55678058761&device=m&matchtype=&network=g&gclid=CM2f4r-M1sYCFchffgodsHkOVw These are the nicer versions, we use them in the studio.
http://www.gabrians.com/product_p/AKG-K240STUDIO.htm?gclid=COqUkMSM1sYCFQenaQodhe4Dbg