Strange, Im sure I have answered you, must have missed the post button. There is no issue with a second set of RRCs if you have enough bandwidth, but you must use a new set of port numbers and setup portforwarding for them. I think you can decide in the TM-D710 if you want both RXs in same speaker or if you want them in separate, both alternative can be handled by the RRC. I have used TM-D710 remote my self, The main functionality is perfect but there is a few limitations, the buttons on the mic do not work, and there is probably some limitations with the APRS functions as the modem is located in the frontpanel. If you need those functions the IC-2820 might be a better choice as it is fully supported.
73 de mike