HE-5s have a few things going for it.. a reasonably decent bass quantity/quality ratio (compared to say K701), great midrange, and massive amount of treble energy (Compared to the K701/2, the HE-5 have a lot more treble) It's also got a pretty decently sized soundstage.
What's your budget btw? I'm not sure if you're looking for a budget headphone, given that you want to sell off your headphone (but you seem to like it's sound signature), but your amp is also the very nice Sonett
While I haven't read up on the new HE-5LE or HE-6, some headphones off the top of my head would be the PS1000 or T1, given the HE-5's more musical/natural (read:colored) nature. Budget options I'm not exactly sure, perhaps IEMs?