Multizone speakers
jchag,
There are a couple ways you could setup your multizone system. It is possible to connect the (5 pairs of) zone speakers to the powered zone 2 on your receiver, but you won't be getting much power, probably 10 Watts per speaker. Try to use the old prologic receiver as an "amp" conected to the line level output on the 804. Assuming that it can handle 100 Watts per channel, you will get about 20 Watts per speaker which is probably adequate. This will also free up the 804 for 7.1 in the main HT.
If this is not loud enough, consider using a Behringer A500 ($180) as the amp and configure your speaker selectors to create a 4-ohm load. The Behringer should deliver 40-50 watts per speaker.