How many Logitech Duets on one system

I run 6 with no problem. I never have all 6 running and only run a pair in sync mode when entertaining.

Hard to say until you try it. I really don't know the limitations on the units. I currently run two and have an extra for another system that is not set up and have not run three at a time. It boils down to how many you would be running at any one time in synchro mode. The biggest limitation will be your server and your router in terms of serving the data at any one time to each zone. If you are only running a couple zones at a time, I don't see why it wouldn't work. The other question is why not move to the Touch as it supports higher res audio. I saw that Logitech has discontinued the duet, but there may be deals out there on it. I'd check w/ Logitech or check the forums to see about numbers of units that could run off a single system. Good luck let us know what you find out.