Using the speakers to listen to other componest of my stereo system

Yes, you could have two complete systems crossing over to each other but the sharing will only be in Stereo either way and you will have to decide which one you want to be the Home Base for the other. I would think the deciding factors would be 1) Do you want multiple channel sound; 2) Are your existing speakers far superior to the DAV-FR1's?

DAV-FR1 in charge: If your receiver has one unused Tape (*) or Line Out pair, run a pair of RCA cables to the DAV's SAT Audio In and when you want to hear its attached program sources choose SAT on the DAV. You could also leave the 4 speakers in place or arrange them to augment 5the DAV and hear them all.

* If you use a Tape Line Out pair DON'T select the Monitor on the source or it will de-select any non-tape source going Out to the other Receiver.

Your receiver in charge: Run the DAV's Audio OUT (L/R) jacks to any Line Level input on the receiver (AUX, Tape In).

If whichever direction you wish to use doesn't have a spare Line Input or Output get yourself a pair of RCA cable splitters of the appropriate gender (one male end / two female ends) and share the jacks. Just make sure whichever source you're NOT intending to hear has something inactive selected.

You could even have both. but you would have to take care to NOT induce a circular loop by having each selecting the other as a source.