Well, I'm about 90% of the way to figuring all this out. Thanks all for your input...

I spoke to Sony Tech support again and discovered that the way to switch the receiver to the 2nd Room mode is via a combination of keystrokes on the Remote Control (which is only mentioned in the Remote Control instructions -- seems stupid not to have this info at least referenced in the Receiver manual).

I've got things to work okay by using a separate amp/receiver (as described in the post above). Once I get the time, I'm going to check out this Remote Control maneuver to see of the double-labeled speaker terminals on the back can be used without the need for a second amp...