Hi
The Port is just another source component (like a CD player). Therefore adding a sub to your AVR input will capture the low end coming from the Port as a source.
Your sub should work with any source component connected to your AVR.
Without researching your Denon S660H getting surround sound should be straight forward. On the back of your AVR there should be connections for rear speakers. The process is the same for any AVR capable of wiring for Dolby Digital 5.1; or better, system (i.e. front_left/center/right channels / rear_left, right channels and sub). Your Denon S660H manual should walk you through the setup and what speaker components are required.
You will only get Dolby Digital 5.1 (or better) sound from a DVD/Blu-Ray disc or a streaming service wherein your TV can send the sound to your AVR. Today's TV’s and other AV sources use HDMI cables to send the AV data for Dolby Digital 5.1 to an AVR.
The Port will only support 2-Channel stereo.
Thanks I appreciate the feedback - this answers my quest for sure about the Port and Sub thanks again.
I think I found the solution to my problem regarding the port and replicating the sound out the rears. I realize I was not clear I have the rears already wired in but I just wanted them to play music same as the front L+R speakers. I think configuring multi channel stereo will do this.
Thanks again!!