With the Esoteric K-03XD SE now having the Esoteric Master Sound Discrete Clock for Digital Player discrete clock module, I would suggest first evaluating the performance through break-in without an additional master clock. I would also suggest the same for the AP20. If you are primarily interested in the Aurender MC10 clock, I would hope your Aurender dealer would support an in-home audition or purchase return should the MC-10 not meet your cost/benefit expectations.
I also like @oddiofyl suggestion for Mutec Reference clocks. Even the lowest cost Mutec REF10 Nano has very good specs and offers both 50 and 75 Ohm outputs, 2 each. The top of the line Mutec REF10 SE120 has even better specs and 4 more available 75 Ohm outputs. Pricing on the Mutec models is also considerably less.