If you want to stream to an existing Sonos speaker system, I highly recommend the Victrola Stream.  I just bought one and it is super easy to connect.  Has built in preamp and doesn’t require any direct connection (i.e. to an existing speaker, a Sonos port, etc.). I couldn't be happier with the Victoria Stream (I bought the Pearl version).

Hi

I think you’re overthinking everything. The Sonos edition Project Turntable is an excellent buy. I have the carbon. 
The turntable can be used with non-Sonos equipment like an AV receiver with phono input.

The phono cartridge is Moving Magnetic (MM) which is found on most turntables. There is also a Moving Coil (MC) cartridge which are more expensive. Each type has its advantages and disadvantages. So called “Audiophiles” most likely prefer the MC cartridge. If not for sound then for bragging rights. 

Both MM and MC cartridges have entry level, mid range and high-end choices. I upgraded the entry level Ortofon 2m Red MM cartridge to the Ortofon 2m Blue MM cartridge. The upgrade did make a difference in sound quality (IMO) not that the sound was bad with the 2m Red. The next step in the Ortofon line is Bronze which was a bit steep for my pocket. 

Learn more about the Ortofon 2m cartridge series at the link below:
 

https://www.audioadvice.com/videos-reviews/ortofon-2m-phono-cartridges-series-overview?gad_source=1&gbraid=0AAAAADRzHk_qoaqDCEgXwFbr_MWrx6WY1&gclid=EAIaIQobChMIkKLa0ubsgwMVAc_CBB35iQXxEAAYASAAEgLNTfD_BwE

The Sonos Project Carbon edition comes standard with things that are upgrades on others. Such as the weighted acrylic platter and carbon tone arm. 
 

The link below may provide more info you’re looking for regarding the turntable itself.

https://www.crutchfield.com/S-wmyXcBPk7j8/p_2521130039/Pro-Ject-Debut-Carbon-EVO-Satin-Walnut.html

I just purchased this Sonos Edition turntable and the Era 300. I have a USB C to 2RCA Male Stereo Audio Cable which would eliminate 2 different adapters. Seemed like a better set up but it is not working. Is the Sonos brand  line-in adaptor really required? I have another non-Sonos brand 3.5mm to USB C adapter that doesn’t work either. 
The preamp is set to Line-out. Thanks for the help. 

Hi @House of Toad

The Sonos line-in for Era 300 requires the Sonos branded adapter. Click the link for FAQ’s.

https://www.sonos.com/en-us/shop/era-300
 

Hi,

I recently bought the Sonos edition Project Carbon and connected it to my Era 300 with the same set up described above, Project RCA connected to their RCA to AUX adapter, connected to Sonos Line in Adapter. 

I hear a humming sound that increases and decreases with I raise or reduce the volume. Even when turn off the record player the sound persists till I don't stop it on the Sonos App.

Any suggestions? Could this be an issue with the RCA cable or the inbuilt pre-amp?

50 or 60 cycle hum? It is likely a power supply or grounding issue.

Try flipping the power cord in the outlet, one device at a time and see if any combination eliminates the humming.

Found the fix. The Sonos edition has a phono - line switch that was hidden. Flipped that to line and it worked.

Thanks!!