Tessi and VoIP

I'm building a wishlist. We are considering dumping our antiquated telephone system in lieu of VoIP. I have heard from past conferences that some orgs have been successful in tying Tessi into the VoIP so that the constituent screen autopopulates in the box office when the agent takes a call. Is this possible or was this a "nice to have" item? Are there any other Tessi-specific advantages to go VoIP? I'd like to get a bit more info on this.. anyone willing to share ideas and thoughts? Thanks!