[jetpig]

The ATH-m50 is a great start. I'm in the same mid-fi ballpark with my DT770s. The next step up in the same vein (closed back over ear), according to the internet at large, would be the Mr Speakers Mad Dogs. They're a custom modded headphone that gets rave reviews all over. If you wanna branch out a bit, take a look at the Sennheiser HD 5xx or 6xx series. The HD 600 and 598 specifically are considered benchmark headphones, maybe not the absolute best of the best, but very good headphones that many can refer to for comparisons. They are open back and very well regarded. Less bass because the low frequencies don't have anything to bounce off, but more space between sounds as they have more air to work with and move. There is zero isolation though, you hear everything around you and everyone around you hears what you hear, so they're more of an at home set.

In order to prevent further derailment of this thread, check out reddit.com/r/headphones and head-fi.com. Head-fi starts to get into the snake oil side of audio gear with talk of cables making a huge difference and what not, but there's a lot of good info there too.

Sorry about your wallet....