I'd like to see, or hear for myself, the FXT90 vs. the Sonocore COA-805 dual driver(update to the 803 with supposedly better mid/high end). Similar concepts with a bit different designs.
Having had the FXC80 that uses a micro driver with the carbon diaphragm, this design makes sense to me. The FXC80 tried to be a good phone but the driver sounded like it needed help. Solid bass and also trying to have crisp detailed treble and good extension on both ends. Kinda fell apart going toward the high end. Some extension, yes. Some detail, yes. But more bright then crisp on the high end with some peaks and the tone/timbre fell short compared to the low end. Really gave me the impression of a small driver in over its head. So, doubling up is just what I would've tried next. They just need to have done it right.