You can assign the last 2 channels to zone 2. You will need at a minimum, a volume control in the other room. Best would be a volume control and a remote eye. This can all be done via a single run of Cat 5 wire. I like the volume with remote built into it instead of having a double gang box for both.
The cat 5 would run from the receiver to the box to the speakers. 3 wires for the remote eye (I think) and 4 wires for speakers. Then, a pair for each speaker from the volume. You can get away with a remote eye only and use a zone 2 remote control (the little one from the 385 or 685 multi zone receivers will work). However, I really like to have the wall volume too.
The cat 5 would run from the receiver to the box to the speakers. 3 wires for the remote eye (I think) and 4 wires for speakers. Then, a pair for each speaker from the volume. You can get away with a remote eye only and use a zone 2 remote control (the little one from the 385 or 685 multi zone receivers will work). However, I really like to have the wall volume too.