I actually own almost all Beyerdynamics models that came up the last 5-7 years, except the T1 (770, 880, 990, T70, T90, T5P). Yes, they are all bright sounding, especially the 880´s (my least favorite) and lack some impact in the bass, except the 990 600ohm that are the most fun headphones I have ever heard (at the prices they are right now, everyone in the world, even Trump, should get one as I consider this the best deal in the history of mankind).
However, pairing them with the A1 amp brought them all (yes, even the 880´s) to a whole new musical level. It corrects the flaws and enhances the virtues of them all. I really don´t know what or how Beyer did it, but the outcome is simply stunning. The bass is deep and controlled, never overwhelming, and the treble is precise but smooth. The T90 specially becomes a sonic beast, achieving the fun sound of the 990 but with a clarity and soundstage I have not heard in any other phones (I also own Fostex RP500 and Oppo PM3 planars, Senn 598, Kef M500, Zik Parrot.
I will buy the Amiron, and I really expect a sonic blast with my A1.