Assuming your Nuvo devices have a sensible input impedance there should be no problem with the Port feeding multiple units in parallel. 

Sonos offer a generous return policy for products purchased directly so you could always get a single Port and simply try it. 

Thanks Ratty.  I wasn’t aware of the Sonos return policy, but that’s good to know.  Regarding your impedance comment, please bear with me for a moment while I confirm my limited technical understanding.  When the output signal of the Port is split, there will be signal attenuation associated with the split.  The more “pieces” the signal is split into, the greater the attenuation.  The question is at what point does the attenuation get so much that the amplifiers can’t adequately process the signal.  This is what you are getting at when you say “sensible input impedance” regarding the amplifier’s capabilities.  Your point is that as long as the amplifiers are of high enough quality that they can accept an attenuated input from the Port, it should work.  Am I understanding this correctly?

Obviously trying it would be ultimate test.  If I do that, are there high-quality splitters I should use that will minimize the attenuation, or are splitters commodities and the specific brand doesn’t make a difference?

You wouldn’t need any kind of fancy splitters to start with. Simple Y cables would suffice. 

A line-level output is basically a voltage generator. If the output impedance of the source is low and the input impedance of the sink(s) is high, there’ll be minimal attenuation. 

If you end up wanting to drive a lot of sinks then, granted, you may wish to use an active (powered) splitter. 

Adding more amplifiers to the same PORT is similar to adding more lamps to a home power circuit. You can keep adding lamps until the circuit current limit is reached and, unless you had some very sophisticated measuring equipment and skills, you would not be able to detect any change in lamp output level as you add lamps.

The science of connecting multiple amplifiers to PORT’s output is a bit more complicated than a simple lamp circuit, but connecting several amplifiers with short cables will not create any issues.

One means of connecting multiple amplifiers to a PORT would be using a spider’s nest of RCA-Y cables. Or, this sort of product.

That splitter box is quite nice!

I don’t have the specs of your amp or Sonos but in general outputs are around 600 Ohms and inputs are closer to 50,000 Ohms so your 4-way split shouldn’t be a problem. 

SONOS Line-Out is in the 50-Ohm range.

Thanks ratty, buzz, and Stanley_4 for your responses.  Sounds like splitting the PORT output to 2,3, or 4 amplifiers should work.  Thanks buzz for the reference to the SBC splitter box.  I’m going to try the PORT in conjunction with the 1 to 4 pair SBC box to combine two zones that use four amps and four speaker pairs.