I would surmise the difference could be channel tracking, especially at low volumes.
The DACT would seem to have the better tracking,
The other difference is that the RK50 has seamless volume control whereas the DACT could be a problem for some who would like a low volume level between two steps in the DACT.
A Khozmo (If they could get their quality control in order) with twice a smany steps as the DACT could be a good compromise. Caveat Emptor.