The only problem I've encountered related to the fact that one of my Rios in ethernet connected, the rest are home phonline connected. Per the user manual:

Limitations

HPNA or multi-homed hosts: if your host PC has more than one network card (e.g. both hpna and ethernet cards), tRio can only synchronise playback between Receivers attached to the same card. Receivers on other cards will not appear in the Listen To dialog.