Howard Nurse, W6HN
Hi Garry and welcome!
I believe both the 7610 and 7300 support the CAT Power Off and Power On commands, therefore RigPi will accomplish both with both radios. Furthermore you can have the 7610 and 7300 connected at the same time using two accounts. Control is completely separate, including a shared or unique log, spot source and filtering, and rotor control. Open one browser for each account.
Normally you will use a USB port on RigPi to connect your radio. That might conflict with your statement that the radio USB port is already committed. Tell us more...it might be possible to use a CI-V to USB cable in place of the USB port on the radio.
RigPi can also control an AC power switch if all else fails (see CommCat Help).
73, Howard W6HN (from the 2019 Dayton Hamvention)