[nbohaychuk]

I've been listening to Beethoven a lot lately and I've been noticing flaws in the sound reproduction of my ATH-M35. I've been switching between my ATH-M35 and ATH-M50 on my home setup to find the differences between the two headphones.
 
Portable: iPod Classic > FiiO E11 > ATH-M35
Home: Creative X-Fi HD USB > ATH-M50
 
I love my ATH-M50, but I wish my ATH-M35 sounded more like them. I find the mids in the ATH-M35 just not quite there and I find that the mids sound muffled. The soundstage on the ATH-M35 is also not as good as the ATH-M50 and it's bothering me a lot. The noise isolation in the ATH-M35 also isn't quite good enough since I use my portable rig mainly at school in class or on my spares.
 
I'm looking for headphones with good noise isolation, soundstage, and (I think) slightly emphasized mids $250 - $300 and I live in Canada, so I'll probably have to order them online. I use the M35 on the go because I consider them more portable than the M50, but that isn't much of an issue if I'll get a significant upgrade in sound quality.

 

[nbohaychuk]

They aren't full-sized, but the Sennheiser HD25-1 II and Beyerdynamic DT 1350 have caught my attention, but I don't want to lose the wider soundstage of full-sized headphones for portability. The Senns also don't seem to have the sound signature that I'm looking for.