Hi guys.  Please forgive my ignorance on this topic, and help educate me.   I've never attempted anything like this before.
I'm starting to build a small additional stereo system for the other living room in my house.  This will just remain 2 channel most likely.      
The goal:  I'd like to be able to stream music over the home Wi-fi network and have the same song play simultaneously from both systems, like for Holiday parties.    Is this reasonable/doable?
I have one Denon X4500, which is currently a preamp in the main theater.  I am planning to purchase a true (better hopefully) pre-amplifier/processor to process in my main theater, and move this Denon receiver to living room #2, in which it will power a small stereo system.
Questions:
1) Can HEOS do what I am asking for?   Can it stream music from one receiver/pre-pro, and have it play the same song to a different receiver/pre-pro too?
2)  For this purpose, is HEOS or MusicCast considered better?   Are there any technical/actual differences in Sound Quality... or does it come down to UI/UX and personal preferences?  
3)  If I add a Marantz Preprocessor, will it be able to stream music to both systems?  What level of current Marantz pre/pro is needed for HEOS?  I was looking at the AV8802A, but frustratingly, I cannot see that it even has HEOS.  Can anyone confirm this?
4)  If I add a Yamaha processor, like the CX-A5200, it is going to stream MusicCast.   This poses a problem, since I would have a Denon Receiver in the other room.  Can I connect some kind of inexpensive MusicCast device to the Denon to receive the Yamaha's signal?  What would that be?
Thanks for any clarification... I've never attempted anything like this before.