Don't we have an advice thread?

+1 on the HD600 though.

the on-ear momentums were a bit disappointing compared to the over-ear IMO. kind of boring dry thin sound.

I had a lot of problems finding good portable headphones a while ago, ended up with IEM's instead...
but... Sennheiser Amperior have a bit of bass/treble emphasis with a quite noticeable dip in the upper midrange. not sure if I'd consider it nice balance but they're nice and clear otherwise.
the over-ear momentums are good, much better balance, very slight dip in the upper mids as well but nothing major. kind of warm/not 'clear' sounding at times though.
audio technica ath-m50s are good but I suppose a bit U-shaped frequency response. midrange is a tiny bit muted compared to treble/bass. but I like them. built like tanks as well.
V-Moda M100 aren't what I'd consider clear or good balance but very well-built and good sound. big bass but not overpowering. treble's nice and strong without being harsh. but lack a bit of clarity I find.

I don't think they're 'portable' in the sense of light weight and all that, but MrSpeakers Mad Dogs are great sounding with a bit of bass emphasis (really good bass quality if you ask me). would have gotten if portability was not a big problem. still, worth checking out.
also depends on what you will drive them with though, I think. seemed quite hard to drive.

HD600 is not closed so ignore those. great sound though.

Whoops! I was drooling over the HD600 deal. I should have wiped the drool away so I could have read the words "closed" and "portable"

mad dogs are IMO 1234 times better than the D600 (which I didn't like that much)
they don't have over-emphasized bass at all, just like a 1-2db boost. not at all overshadowing. which I found the D600 to be.