The only pair of phones on your list that I have heard is the DT770s. As a musician myself who mixes and masters his own music with a DAW, I would never, under any circumstances, use the DT770s as a headphone for mixdown and mastering. And for whatever it may be worth, I think they actually sounded dreadful while listening to my music as well. Sucked out mids, grainy unimpressive highs and overwhelming flabby and bloated Bass. Needless to stay, the DT770s didn't last long in my collection. For the particular applications in which you want to use a pair of headphones, and given your budget, I personally would choose the Equation Audio RP-21s any day over the DT770s.
But honestly, the best way to go for music mastering and mixdown is a pair of decent nearfield monitors, such as these for example:
Behringer TRUTH B2031A Active Monitors
Any serious recording engineer will likely tell you the same thing - nearfield monitors are the way to go. If you can get your music to sound great on a pair of nearfield speakers, then you significantly increase the odds that the same music will sound good on all manner of medium used for musical playback, be it a pair of iBuds, cheap car speakers, all makes and models of headphones, mid-fi home theater loudspeakers, all the way up to and including the most expensive esoteric loudspeakers on the planet. The same simply can't be said if you master your music using a 'colored' pair of headphones.
If studio monitors were absolutely not an option for some reason and I had an unlimited budget, I would pick a pair of Grado HP-2s as my pair of mastering/mixdown headphones, closely followed by a pair of properly amplified AKG K-1000s. The reason being that both of those phones have come closest (to my ears) to a pair of nearfield monitors out of all of the headphones I have heard or owned in my entire life.
So yea, if you can stretch your budget to $300, then I would suggest getting a pair of decent monitors for studio mixing and mastering, and then supplement them with a pair of decent headphones for music listening enjoyment with any money you may have left over. Good candidates for $99 or less would be Denon D-1000s, RP-21s and Alessandro MS-1s, for example. If you are still adamant about using a pair of headphones for everything, then the RP-21s would be a decent choice. Even though they are a bit colored, and not exactly nearfield level phones, they were created for studio work, and to my ears, they would do an 'ok' job when used for mixdown and mastering.
Good luck.
