Greetings!

Reading the link you had for the RB20, that one looks correct. The RB10 seems to be one input or the other. If the RB20 allows for the passthrough.

Doing a quick google for "CD-RB20", I am finding a lot of different places selling them on the web, many for significantly less than your original link. You might be able to find one for the same price you paid for the RB10.