Momentums do sound great, true. Though they have one problem, which is they are too small for my big ears :/ This was the main reason I bought RH-A30, which fit my ears almost perfectly. I also auditioned M50, and loved them, but I decided to pay extra 50EUR and get open headphone experience. I still love their sound. Same driver as M50, BTW. But they are open, and I can't really use them anywhere else than at home. Even at home it is sometimes problematic when TV is on. So I started looking after closed cans, and I found Alpha Dogs, which I wanted badly so I got them as soon as they were available from dealer in Netherlands. Now, are Alpha Dogs better than RH-A30 (and thus M50 as well)? Not really sure. They do sound way more detailed (just listen to violin concerto to prove that) than RH-A30, but they also sound very narrow. I auditioned M50, and yes, compared to RH-A30 they sound as closed cans, but on the other hand RH-A30 sounds more open than any open headphone I ever heard (even HD700). But IMHO M50 still sounded more open than Alpha Dog, and basically had better soundstage and 3D instrument placement (some call it incorrectly (IMHO) imaging). What do I love about Alpha Dogs? They are super comfortable, and super bug earcups fit my ears perfect. But then they are super heavy! After many hours of listening at work (~6hrs) my neck used to be in pain, but now I think it got used to that load. RH-A30 is light and almost as comfy (after few hours of listening my earlobes are in slight pain, because earcups even tough they are wide, but they aren't deep enough). From what I remember from auditioning M50 they were almost same as RH-A30 in terms of comfort, though pleather pads made me sweat a bit. I compared M50 directly A/B with RH-A30 and I definitely heard reverb caused by closed enclosure of M50 earcups, so treble sound multiplied few times. Detail wise M50 driver (RH-A30) provides less detail than Alpha Dogs, but the price is 3 times less, so what should you expect?
Recently I have auditioned some new Senn (dunno the model), but it didn't look as awesome as Momentum (plastic and pleather I think). However they sounded as good as Momentum, and earcups were bigger, as big as M50. I would say they can be new king