I would say Sennheiser Momentum, Sony MDR-1R, or V-Moda M100 as the best closed portable headphones you can get in the $300 range. They are definitely the most highly reviewed ones at least. Since you don't know what sound signature you are looking for and you can't demo it for comfort, just buy whatever you think looks better lol.
I think electronica and music by Hans Zimmer, the M100 would give you a lot of legit bass impact without adversely affecting the mids/trebles. M100 has a bass emphasis (the bass is very well-done) so it will excel for that kind of thing. I personally would say at least try the M100 as vmoda & amazon both have great return policies. If it is too bassy for you, then you will have a better idea of what sound signature you want. I really think you should try these first, because I really loved the sound signature of them personally.
The MDR-1R & Momentum are more mid-centric so audiophiles like TheReem who appears to like more flat sound would probably recommend those. I would imagine Shure SRH940 is even flatter. MDR-1r is supposed to be mid-centric with warm bass and the Momentum is often described as technical and balanced throughout. Slightly more bass than normal sennheiser sound though, but less than many competitors.
I wouldn't get the AKG K550 for portable use as it is pretty big and the wires are non-detachable. AKG K551 is basically the same thing but detachable cables. AKG K550 also has a very weak bass compared to what an average consumer would want. For producing/mix, the less-emphasized bass is great as you can hear the treble detail better, but for portables you probably want more bass to help isolate noise & you need it emphasized to hear it over road noise. In my personal opinion, Mad Dogs won't be very portable (bigger than others) and they sound best with a amp, which would be annoying to carry around. Beyer DT880 will also look really crazy big on your head & probably won't be comfy to wear around your neck.
I personally think the M100s would be the best choice for you as the extra tight bass impact might not be great for TheReem as he wants really flat sound, for most average people, u-shaped sound signature is sounds really nice for their music. You will legit feel like you are watching the movie again listening to Hans Zimmer on the M100s :)
Happy Headphone Hunting & I hope you find what you are looking for.
Edited by money4me247 - 3/3/13 at 2:01pm