Well i bought the k550 and so far i am enjoying them.
Good sound, enough bass for me and i must say when the song calls for it they do shake on your head also it just has this lean, deep, full, spacious sound that is clean and clear and smooth.
Sometimes with the way it sounds it makes me jump sometimes exactly as being spooked, no other can of mine has done that before (dt 48, dt 150, dr 770, dt 880, dt 990, k 701, q 701, k240 mk2, k242, hd 555, hd 650, t50rp, ath m 50, hd 25 ii, hfi 580, pro 900, ultrasone proline 2500).
Needs a good seal as you know, sounds like an open can, good isolation, easy to drive yea..
I dunno it just sounds beautiful can see why people praise them or love them.