I was at my local magnolia on Sunday listening to home and mobile headphones that they had on display.
As for the mobile, the two that stood out to me as having the best fit and sound were the B&W P7 and the Sennheiser Momentum over ear headphones.
The B&W's were over your budget at $399., but the Sennheiser Momentum over the ear phones were at $299.
They both sounded really good and they both had a really similar sound to me. I might give a very small edge to the B&W's, but each sounded really nice.
As an aside, they also had the momentum on ear model, and after going back and forth with the over the ear model I just didn't like the fit and feel of the on ear model at all. The sound was similar but didn't seem as full and rich as the over the ear momentums.
Finally, they did have the Denon D600 on display, and I thought they were very comfortable and really nice sounding headphones. But they were not as portable in that they weigh a lot more that then momentums and you feel it. I think they weight 365grams and the momentums are probably around 200grams. But again, the Denon's are very comfortable. The sound was very different between the two as well. I really liked both, but the Denon's have a really "live" (as I don't know what better term to use as I'm a newb here..:) sound, like you are actually at the concert in the audience, while the momentums and B&W's have a really tight close up sound, like you're listening through the soundboard in a studio. Hope that helps.