thanks again for all the responses. I really appreciate the help!
...so I recently ended up getting the Momentums - they sound great, they look cool, they're light weight, BUT - as many others have stated, they get really uncomfortable due to the small cups. something about it hurts my right ear within an hour of wearing. really, really unfortunate since otherwise, they are super comfortable! the leather on the cups with the memory foam feels great and they are fairly light. they have the potential to be the kind of headphones you forget you are wearing, but with a serious flaw on the small cups. ...also, they don't fold in any way at all. I recently flew with them and had to keep them around my neck since I didn't feel good about putting them in my backpack.
...so then I stumbled upon a pair of Bowers and Wilkins P7's for a good price (used) - great looking, seriously well built, classy, BUT - a little "clampy" and somewhat heavy. not as comfortable as I'd like, but no specific issue like on the Momentums -maybe a keeper, but I'm not so sure yet.
both sound fantastic. Maybe the P7's are a little better to my taste. good bass, great sound stage - aside from the comfort, I had a few moments (with both) in which I forgot I was listening through headphones and not my monitors WITH the subwoofer on. that's a great sign.
I ruled out the 545's since they don't seem too portable and I've read that they lack bass a bit. I'd still like to try them, but I can't seem to find a place to do so.
...anyhow, my search (somewhat) continues....