The Port is usually what is used to connect a receiver to the Sonos system. Usually, a tape out from the receiver to the line in on the Sonos would work. You could then also send the Sonos signal to the receiver by connecting the line out on the Sonos Port to the tape in on the receiver.

That puts the receiver’s signal in to the world of Sonos, and it can then be sent to any Sonos product you have in wifi range. 

Given that you’re talking about an “outside” area, you may want to avoid getting a Sonos speaker altogether, and instead replace the Port with a Sonos Amp, which can then drive your own third party outside speakers. Sonos themselves don’t make outside speakers, but they do have a co-marketing agreement with a company called Sonance, although the Amp would power most any outside speaker on the market, making sure you match power and impedance. That way, you can keep the Amp inside out of the weather, and have the speakers outside without worry. 

Why are you considering adding products that will not “talk” to the one that you have? 

The Node is for the stereo system, but if it’s easier to just buy another Node to link the outside zone, I may just do that instead. Sonos just came recommended, so I wanted to see what the possibilities were.

Is tape/record out the only output that would send a signal from the preamp to the port? Or would a simple analog out suffice?

Any line level output would suffice, yes. Hence my use of the word ‘usually’. But that only connects the output of the receiver to the Sonos ecosystem, and you lose the other half, which is the ability to push the Sonos data to the receiver. May not be an issue for you.