Most of these clock inputs are word-clock only, which is simply a bad idea.
The Overdrive already has I2S input, which includes word-clock, bit clock and master clock. I am already using this with my Off-Ramp and soon my new Interchange network renderer. Separate external master clocks (2 needed) are only interesting if the external clocks are a lot better than the internal clocks.
A word clock output however is a much better idea. This way the DAC always becomes the master., but the source must have word-clock input and be able to sync to it.
Steve N.
Empirical Audio