I'm a Linux Systems Administrator with experience in Debian (and derivatives) RHEL (and derivatives such as CentOS) as well as Gentoo and hardened Gentoo. I'm a VOIP consultant, and I've done this exact setup many times, including an installation today. I'm comfortable with compiling the kernel if your distribution of choice does not have an openvz kernel package, and have scripts for deploying Trixbox to VE's (which you will get so that you can add more VE's quickly and easily)