Mike, you just daisy-chain them using the RCA connections.
One is master and one is a slave. You route the RCA/analog outputs from the slave to the master and then the same type of cables to your preamp. They are also connected to each other via a 1/8 inch mono plug (for serial communication). I think it comes with the player.
My point was that one of the reasons why I had resisted these devices for so long was the very long lag time between disk changes (10-12 seconds?). However, when you use two of them together, one plays while the other one loads the next selection, so there is no lag (assuming that your sequence - whether random or not - can alternate between the players).
However, to do this, you must use the DAC's of the player rather than sending the digital output to the DAC's of your Rotel. Like I said, it sounds fine to me, but your ears, equipment, room, karma or harmonic balance might be better than mine.
This scenario invites a bit of strategy as to how you load your disks. You may not want to have all of your similar music on one player, for instance. Also, be sure to note that it is very important to balance the loads within the changers (don't put everything in slots 1-300 and leave 301-400 empty).
You can assign each disk to one of 8 groups of your choosing and then play just one group, or all disks. You can't play everything except one group, however. I think there are others here with similar setups (BrotherBob, Capn_Pickard, others?).
We are a whole community of "that guy" - StPatGuy