Hi Andrew. It is almost as if I paid you to post this! We (Lotus 911) offer exactly what you are looking for: A single server with a VOIP PBX and Sametime fully integrated with each other on par with the "Sametime Unified Telephony" solution that IBM offers for the larger VOIP providers. There is no smoke and mirrors. This is IBM Lotus Sametime and our open-source PBX with our standard integration and extended Sametime features built-in. Go to http://www.lotus911.com
and click on the TruePresence icon for more info. You can also contact us through our web site to start a more detailed dialog.