Not sure this is the right place to post, but if you are interested in trying Xen with VGA passthrough, have a look at this:

The how-to uses Linux Mint, which is based on Ubuntu. It should be easier to accomplish using Ubuntu, since Ubuntu has LVM support from within the installer.

Feedback is welcome. If necessary, I may modify the how-to for Ubuntu and post it on the Ubuntu forum.

Given the right hardware, VGA passthrough is real cool. My Windows 7 VM feels like running on native hardware. Here a benchmark:

My graphics card is a bit weak, though. Not meant for gaming.

Other alternatives are kvm, which is developing fast. kvm will probably require a 3.9 kernel for VGA passthrough to work nicely (even with some Nvidia cards), so kernel compilation may be necessary. This how-to may help: