Just a suggestion Pat, if you'd rather not pay for Vent slots.
http://mumble.sourceforge.net/ (http://mumble.sourceforge.net/)
Open source, low bandwidth. Up to 500 slots.
My favorite CS ZombieMod server is running this and it sounds just as good or better than Vent.
Interesting. I am unsure I could get guildies to deal with FOSS packages, though. Ventrilo is not too bad.
Mumble is great, we've been using it for arena for...probably over a year now. Lately have had some server issues, not totally sure what that's about. I find that the quality is a bit lower (nothing to write home about,) but the response time seems much better.