One thing that might fit is the Koss Pro DJ100. It has great mids, and though the bass is a tad emphasized, it's not bloated and (in my opinion) doesn't bleed into the rest of the spectrum. Some have said that they don't sound very good without an amp, but I think they work fine out of onboard sound. An amp and/or DAC does improve them, but not as much as some make it out to do. They do lack for soundstage a bit, but then all of my other headphones are fully open, so it's hard to make a good comparison.
As far as size and weight go, they're not particularly big or heavy, though the cups are aluminum instead of plastic, which does increase the weight a bit. Not to the point of being uncomfortable though. the cups are a bit shallow, but this can be improved by stuffing some padding (or in my case, a strand of network cable) under the earpads to lift them a bit. With them like this, I regularly listen to them for 8 hours straight at work.
They retail for around $80.
You could also try the Creative Aurvana Lives, which are a popular recommendation in this price bracket. There's even a comparison thread between them and the DJ100s somewhere on the forum. I haven't heard them though, so I can't really comment on comfort or sound.
Thanks for the quick reply! I read some reviews for both, and they seem fitting. Some people seem to be complaining about the cable durability of the CAL though. Does the Koss Pro DJ100 have a spiral cable?
Do you need them to be portable? On the portable end, I haven't really heard of any headphones known specifically for soundstage... A couple options to look into might be the Creative Aurvana Lives (CAL!), which are closed or the Superlux 668B, which is semi-open. Both go for around $60 and have good reputations.
No, I wasn't looking for necessarily portable ones since I mostly use them for home listening. By soundstage do you mean a distinction between the instruments?