Once again, I appreciate your advice. I am getting a Macbook Pro in the spring, so I will see how it fares with powering my M50s, because that is what I will be plugging them into. I heard the MB Pro has a decent enough built in sound card and DAC. It would probably be better for me to get the cans (DT770s), and then see if I need an external amp/DAC or not. Should I make the FiiO E11 second in my list to the E07K?
Since you said they are well built, should I not worry about getting refurbished DT770s for a retailer on ebay?
When the time comes for me to expand my inventory to open backs, is there a definite sound difference (such as in bass amount and highs) between the Sennheiser open-backs like the HD598, HD555 etc, and the AKG K701s?
Apple products in general, have a reputation for coming with decent audio support.
The E11 would make a good second choice.
Hopefully the refurb DT770 seller has a decent return policy.
I'm going to say the Q701 seem to be the preferred headphone for FPS gaming.