Best way to install on Gentoo

[uxbod]

I have a good server setup at the moment Postfix, SA, Asterisk and RoundCube webmail but would really like to use Zimbra. The server is a dual Opteron 275 with 2GB RAM.

Obviously my server is already on a public IP and hostname, but I do have a couple of spare IP's so would it be best to use a Virtual Machine (which VM ?) or a chroot ?

I guess using a VM would seperate it from my current setup a lot better ?

All help greatfully received and appreciated.

[uxbod]

If I choose the CentOS route can I use the 64bit version of Zimbra ?