Well, the TC Sounds 12" are here now and they add $1500 to the $14.9k price of the Bybeed RM50s. The main difference between the Eminence version and the TC is Xmax (15mm vs 24mm) and that there is no plastic dustcap on the TC. The TC has a one piece solid cone with no dustcap and is vented out the rear. The former and voicecoils are also different.
As for sound, the TC sounds better, but the Eminence is a great performer. Both drivers have diecast frames and large, rugged motors with 140oz magnets. The bass we got at CES was stupendous. Chalk it up to the stiffness and integrity of the cone material.
At CES we used a 220Hz/24dB lowpass filter from the modded DCX to suppress the metal cone's breakup mode, located at 1600Hz.
I'm glad Clement Perry liked our sound and hope other press will report equally well.