Add Sonos to house with wired speakers in 12 zones

Here’s a manual for the SI-1230 and SI-275

Can you give us model numbers for the top two Niles boxes? Are there any in-wall Volume controls? Unless there is current provision for In-wall controls for each area, running the wires for this would likely be a major project.

Where is the Volume control for the six speakers connected to the top box?

in order from the top

SPS-6 

MRZ-6

SI-275

SI-1230

onkyo TX-8511

6 of the zones/rooms have Niles control pads which control volume, source and skip tracks (maybe as haven’t tested if they work). The other 6 zones/rooms only have a volume dial. 

The control pads are connected to the MRZ-6. Are the other rooms using in-wall speaker Volume controls? If so, pull one of the controls and get a model number. With the proper in-wall controls that SPS-6 is extraneous. At best it would then be a simple junction box. While there is no immediate need to trash it, depending on the Volume controls used, it was never required.

Yes the other 6 rooms have a volume dial. So in total there are 6 control panels and 6 volume dials. 

The picture is inconclusive. The model number will tell the tale. An “impedance matching” control might incorporate a small switch or set of jumpers that can be set to safely interface multiple pairs of speakers to an amplifier. Presently, most controls that you’ll encounter are the impedance matching type with jumpers or a switch. When this system was installed other types of controls, some without a switch, were common.

Are any speakers connected to the receiver? It might only be used as a remote controlled input switch.

unable to check until later but I believe all the speakers are connected to the top 2 boxes (SPS-6 & MRZ-6)

I think Buzz is taking you down the right path in figuring out exactly what equipment you have to work with.  However, just an FYI, you won’t need an Amp and Port for each zone, you’ll only want one or the other.  Both have all the ‘smarts’ built into them.   The amp is the right choice if you want to power your speakers without using a 3rd party amp/receiver (which you already have) and/or connect a TV source.  The Port is right choice if you already have an amp/receiver and/or have an aux input source, like a turntable or CD player.

I would guess (didn’t look at the user manual too long) that you could use your existing equipment and just add a Port or two as input sources for the system.  You would still use the existing controls for everything else.  If you went with amps, replacing all of the existing system, you’re likely going to need at least 6.  The amp usually is for a pair of speakers, but you can use it with 2 pair  if your speakers are 8 ohm (likely).   Impedance matching switches could allow you to hook up additional speakers to a single amp, which is part of why Buzz is asking about the switches.  Each amp is just one zone at one volume for Sonos, but your switches would allow you to control the volume for each room.