Best Passive Mixer Design?

To mix the outputs from three CD carousels, I need to construct a cheap passive mixer. (This is temporary measure until Colby has the digital crosspoint switch ready.) Colby's own design for such a mixer, at the link below, calls for using 2K resistors in series with the output circuits to isolate the CD players from each other. Another design I have seen is identical except that it calls for 4.7K resistors. Can anyone comment on the relative merits of 2K vs. 4.7K resistors in a circuit like this? In other words, what are the tradeoffs? I realize neither will be the greatest piece of audiophile gear ever devised, but given the limits of passive mixers I'd like to use the best design.

The CD players in question are a CDP-CX350, a CDP-CX270 and a CDP-CX250.