Help with virtualization.

[1clue]

Hi,

I've been messing around with multiple desktops for awhile, and I finally got everything so messed up I want to scrape it off and start over.

Here's my requirements as concisely as I can get it:

1. This is a desktop system at home. Basic system specs in my signature, but disks will be wiped out and started over.
   
2. I'm an experienced Linux user with a long time experience, but not deep knowledge.
   
3. My girlfriend is a novice user who just wants to use gmail, facebook and all the rest of the junk people use. Her Vista laptop keeps getting viruses so it's essentially worthless.
   
4. I need a simple, reliable host OS that is stable and trouble-free.
   
5. I need good video performance on most of the VMs. This includes flash and other streaming media.
   
6. I mostly want a Linux distro that I can get several isolated desktop environments/window managers on, without getting polluted by the other DE's and WM's. These images will be used mostly one at a time but will be what I use on the desktop.
   
7. I also want to install brand new Linux/FreeBSD/etc distros to see what they're like. These can be VirtualBox.
   
8. I will need to run a couple Windows VMs for my work, to test how software I write interacts with Microsoft clients. These can probably be VirtualBox.
   
9. I want to use all my available cores for compiling on Gentoo, when that comes up.
   
10. This system WILL run both free and non-free software. I have no problems running commercial drivers or software I need to pay for, but I'm not rich so spending a huge amount on a virtualization solution is not in the cards.
    

I've used VMware on Windows, Mac and Linux as hosts, VirtualBox on Linux and Parallels on a Mac. I've messed with KVM but never really got it right.

I'm not sure what to put in as the host. Some of the VMs will need to be run continually, but most will be on-demand.

I was thinking maybe that I could use OpenVZ to install a basic Gentoo, then have containers which each contain a desktop environment. Not sure if I can share the user list and documents but not the home folder/settings between these things.

Any recommendations?

Thanks.