Usually you should work with a qualified Polycom Reseller as any advise without knowing the layout of the room is a tricky one to make.
Is this a analog Line or a SIP Installation?
We have plenty of different Conference Phones in the SoundStation range that offer external Microphone connections to suit larger meeting rooms and are full duplex in order to suit a conference setup.
Polycom Global Services
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's