I am not going to lie a headphone that has good seperation and soundstage like an open back with good details and bass is going to either A) Cost a lot more or B) is going to be hard to find. You are going to have to decide if either bass or details, soundstage, and seperation are more important to you.
I personally found that the ATH M50s were a bit harsh treble wise, and I personally do not think it was very detailed. It has a good amount of bass, but that feeling "I have to have bass" wore off on me after a while. I find the bass a bit uncontrolled imo. The sound stage quite honestly sucks. Don't get me wrong it sounds like I am bashing, but the main things these have going for them are the excellent build quality and the "fun factor" these have. Excellent starter pair of headphones (I started off on these for about 2 years), but if you want the higher grade of sound you are going to need to throw down more money.
Anyways I owned both and did side to side comparisons. When compared to the M80s, I feel that the M80s edges out the ATH M50s in nearly every way with a very similar sound signature. The build quality is solid, but I am not sure if I liked the feel of them as much. The M80s seem like they can take the same abuse but the m50s are so much heftier that they feel like a tank in comparison. They also scaled surpisingly well with better gear, in comparison to the M50s which most of the time just sounded the same. However all this being said the M80s were not a comfortable headphone for me in any shape or form. The clamping force was too tight and it was really hard for me to keep a proper seal at all times. Also to take into consideration is that these things are SMALL. I was shocked when I opened the box to find these tiny things.
I would also like to throw the Logitech UE6000 in the ring. I only had a limited time with these, but the sound reminded me of the V Moda M80s (edging out the M50s in many ways) but perhaps a little more contained. As in the bass was not as overpowering and did details a bit better.
None of the headphones mentioned above did I find good for gaming or movies. They just did not do details or have good enough sound staging for me. Otherwise for primarily music these are good starter "fun" headphones. I think you are going to have to sacrifice a good amount of bass if you want more details and separation.