The AD700X series will be fairly bass light, from what I understand (I have only heard the A700X and A900X). DT990 will have some bass emphasis and is also known for fairly bright treble (I've only heard the DT880 and DT770, but based on comparisons I have read).
If you wanted something more in between, the Soundmagic HP200 has good reviews:
Impedance is 32 ohm for the HP200, so easy to drive in that regard, although sensitivity is a little low. Might need an amp to reach the volume that you want and to give you better dynamics. But should sound good on most portable devices without one.
OH HEY Yea the HP 200! I really like the HP100, try the HP200, and yea the DT 990 is rather bright, which is why it pairs nice with the vali. And I hear you on the tube rolling,