cel4145
Headphoneus Supremus
The Audio Technica A900X also seems really great! How do they compare to the AKG K271 mkii? Those two may be the ones I'm deciding between.
I don't know about the K271, but I do own the HFI-780 and M50s along with the A900X. I find the A900X to be a fairly balanced headphone (maybe a slight bit of bass emphasis) with better detail resolution than the M50s and the 780s. The main drawback to the A900X is that they are a bad choice if you need anything portable. They don't fold up and are bulky because of that.
The 780s are actually quite good for a wide variety of mediums for a headphone with more bass emphasis. They have a very warm sound, but the upper mids are recessed. For your music tastes, I would go for the A900X first and then the M50s.
You might also look into the KRK KNS8400, which are studio headphones. The Takstar Pro-80s are currently very popular as a direct from China brand that competes with other headphones in this budget range, yet can be had for under $100. See this discussion thread: http://www.head-fi.org/t/585356/the-takstar-technical-pro-gemini-greathon-thread Nice thing abouy them is that would leave you some of your budget for an E11 amp or a better DAC/amp for use with your laptop, if you were interested in that.