Not clear what you are trying to achieve.
Google Voice uses XMPP, not SIP.
Your IP phone probably uses SIP, but not XMPP.
OBi ATAs can use XMPP and SIP.
So OBi - GV - Avaya is not going to work.
OBi - GV - DID from an ITSP - Avaya will work
or OBi - ITSP - Avaya will work
or OBi202 - Avaya will work.
There are probably others depending on what end result you desire.