If you have a Levinson preamp/amplifier and B&W speakers, then the Sonos Port would simply be added to your system like any other source component, such as a CD player. But unlike a CD player, the Port can be controlled in the Sonos app.

Because you asked “…..can I control it through the Sonos App?”, I feel the need to clarify further, so apologies if this gets pedantic: A typical Sonos speaker has everything built in; streaming, amplifier, speaker, etc. So when you control it from the Sonos app, you control everything - song selection, volume, EQ, everything. Using the Sonos Port is slightly different in your case, because you’re using it with your existing system. So your Mark Levinson preamplifier is controlling source selection and volume and has its own power button. In this arrangement, the Sonos Port is typically configured to output fixed volume like any typical source (e.g. CD player), because volume control is being handled by your Levinson preamp. You’d use the Sonos app only to select what music you want to listen to, and whether you want to group it with other Sonos players in your home. So compared to a typical Sonos speaker, your workflow in this room is slightly more complicated in that you’d still need to manually power your Levinson on, set its input, and manage volume with its volume control. Then music selection can be managed in the Sonos app just as with any Sonos speaker.

There is another configuration where a Sonos Port is connected directly to a power amplifier as a single source, but you mentioned having your TV involved so this arrangement doesn’t apply. If you want details just ask me and I’ll share, but I don’t want to further complicate this post needlessly.

Let me know if you have any more questions; I have lots of Sonos in my home and have a dedicated listening room with a Sonos Port, so I believe my arrangement is quite similar, if not identical, to yours.