A:Answer Hi Frank,
The AVR-S660H is set-up to run a 5.1 speaker system. You can run just a stereo pair instead, or even three speakers across the front (with or without a sub-woofer. The AVR-S660H is not designed to run two main pairs of stereo speakers at a time in A/B mode. That being said, with a 5.1 set-up, you can select Multi-channel Stereo and have the same stereo feed to the rear speakers as you have to the front speakers.
If you want to run two separate pairs of stereo speakers in your home, and you don't need surround sound, have a look at our PMA-800NE stereo integrated amplifier:
https://www.denon.com/en-us/product/amplifiers/pma-800ne
If you prefer 5.1 surround sound, and the ability to drive a second pair of stereo speakers, have a look at the AVR-S960H. The second pair will be run, and assigned as Zone 2 speakers.
https://www.denon.com/en-us/product/av-receivers/avr-s960h