DT770s in 80ohm. You won't be disappointed. I hated the M50s, and got these as a replacement. They work okay unamped, but they really benefit with a little added power. They are also supremely comfortable. It's like night and day compared to the M50s.
Maybe try some Grados if you don't need closed cans?
And yes, you likely will hear a difference. I thought the M50s lacked any kind of mids, and way overemphasized the highs to the point that it was almost painful to listen to. Best thing to do is go try them out. Any HiFi store or Guitar Center will let you try them out before you buy. I don't recommend buying online. It is such a pain to return stuff
After coming from a lifetime membership in the Grado fan club, getting to like or appreciate the sound of a Grado headphone can be a bit hard for listeners. Either some will easily adapt to them and love them, or they will run away from them. I've had too many pair to count, also modified plenty of them, too.