Change of plan:
It would seem there're no "ordinary" BNC outputs on the earlier named WCM-module/expansion board to my RME 9632 soundcard with the desired (internal) clock mode, so therefore I'm planning on upgrading my current RME interface with the Audiophilleo2 + PurePower USB-S/PDIF converter(
http://www.audiophilleo.com/audiophilleo2.aspx), which provides a direct(i.e. without digital cable) BNC-BNC connection to my DAC-9. This is a newer developement briniging with it notable advances in jitter suppression.