2 Sonos systems with one Sonos account

I don't think so.....but i'm not sure. I'd be certain to make sure there aren't any duplicate room names, though. I think the Amazon device would only be looking on the local network for items it can control. But I'm guessing.

With large multi-zone Sonos systems I would avoid the current Alexa integration.

Why?

Simply the Alexa 'ducking' feature. What this does is mute the speaker (normally an Echo device) when you say the wake word "Alexa.." so that the device has a better chance of hearing what follows. Now that seems perfectly sensible, until you see what it does on a multi-room Sonos system.

Alexa (whether on an Echo device or Sonos One) has no idea what room it is in (Amazon don't properly support rooms yet) and therefore has no concept of what speakers might be in the same room and need to be muted. So, with Sonos it mutes the whole system... Obviously in a large multi-room system with multiple people using, this will get more than slightly irritating as every time anyone, anywhere in the house says "Alexa..." everyone else gets silence while that device listens and worse, if they've asked for a flash briefing, as that can go on for a bit while continuing to mute the system.

Strangely(!), on normal Echo devices, if one Echo is playing music, and a different Echo is spoken to, (i.e no Sonos involved) then only the Echo device being spoken to mutes anything that was on it's speaker. In this scenario the Echo device doesn't need to worry about any other devices, and therefore local rooms, so the whole experience seems to work.

As a user of both Alexa and Sonos, what I'd like to get is to be able to group devices by room so that as I walk into a room with an Alexa enabled device I can simply say "Alexa turn lights on" and "Alexa play music" without having to worry about where, as Alexa will know what room it's in, and if there are smart lights and speakers in that room it will simply default to those. That's the big advantage fixed devices have over say Siri, or Google on a phone where knowing what room you are in will be much harder.

Ian_S: Thanks for your thoughtful insight. We are actively working on ducking, but have no information regarding when that feature would be available. Stay tuned.