I've been looking into higher quality headphones for a little while, after some research I am seriously considering buying the Beyerdynamic DT 990 pro (250 ohm). I know that I will need to buy an amp to go with it, but really don't want to spend much more than $100. From what I can tell, the dt900's need a fair bit of power to sound great, and other users on this forum have said that the fiio e6 or e7 won't cut it. I have been looking into the fiio e07k (was looking at the e11, but it seems to be roughly the same amp but without the dac - if the dac isn't as necessary I would consider the e11), and was wondering if you guys think that it would be a good amp to go along with the dt990s. I've also heard that dt990s sound especially good with tube amps, but from what I can tell the cheapest tubes (bravo ocean, schiit vali) are slightly more expensive than $100 and don't include a DAC. I would appreciate your advice regarding the following questions:
1. Do you think that the fiio e07k is a good amp to start with for these cans?
2. How necessary is it that I purchase a DAC? I would most likely be running audio out of my HTC One M8, which I hear has a quality dac compared to other phones. (not sure if that's saying much, though)
3. Do you think that a tube amp such as the schiit vali would provide a significantly better listening experience than the e07k's? If so, do you think that this increase in quality would offset the fact that I wouldn't be using an external DAC?
(Also, I realize that the e07k is portable while the tube amps are not. While I would prefer a portable amp for sake of convenience, I plan on using these headphones at home most of the time, so this isn't really an issue.)
Thanks in advance guys, and I apologize if this has been posted in the wrong place.