Yet another vote for FreeBSD as host. I manage dozens of servers, 99% of them FreeBSD for all the obvious reasons. We don't necessarily run *BSD because it's "free," we run it because it is BETTER. Surely this world would pony up the bucks for quality virtualization software...and the *BSD world may be quite a bit larger than you imagine. Finally, if licensed properly, you would find yourself getting boatloads of help from the broader community.