I will be honest, you posed a question I cant factually answer. I may be able to offer a little information that may help,however. I bought the Beyer DT770 after many months of deliberation. Now when driven from my Fiio E7/9 they sound very good indeed, in some repsects the bass is a little full but I put that down to design, and this is why. Why used with my focusrite 2i2 they sound far less engaging and the bass is a little flat, I put this down to the power driving them. I have also found similar when used directly into my PC so I am guessing that Beyers need a bit of power to get their full potential. I have no experience with the 80Ohm versions, and dont know the difference between the DT770 and the DT990, but I would recommend you dont buy blindly unless you want to invest in some amplification too.
Sorry I cant give you anything solid, hopefully someone else here has more definite information.