[kubuntu] Virtualizing Windows7, what would be the best option?

Hi. Long time since i posted here. I'm still using Ubuntu (now kubuntu 12.04) and i'm still dual-booting (now Win7). A couple days ago i rebooted 5 times just to switch OSs ](*,) so i figured i would have to find a better option. I started looking at virtualization again. Years ago i decided it was a no-option because of poor performances. Now, things have changed with new virtualization options and better hardware.

• I need as close to native speed as possible for Windows7 as well as it being able to use much ram. My most ressource heavy applications run in windows.
• I'd like to re-use my existing windows install, or at least copy it entirely to the VM in a way that won't mess up with proprietary applications activation limits.
• I would prefer to have Ubuntu be the host OS and win7 the guest. I don't like the idea of having Ubuntu depend on Windows to run.

My hardware

• Intell Core i5-2400 (quad core with VTx support)
• 8 GB ram
• 1 TB hard disk with several partitions
• Asus P8P67-M PRO motherboard (i don't think it supports special virtualization features such as IOMMU but i'm not sure how to check it.

I'd like to get the best possible configuration for running both OSs. I've already looked at several options. Probably i missed some :

• Oracle VM Box running under Ubuntu : i fear Win7 will suffer from severe performance drops and i need power for Win7.
• VirtualBox under Win7 (ubuntu as guest) : don't like it much.
• coLinux based solution (andUbuntu & portable ubuntu). Ubuntu would depend on Win and those seem to be abandonware.
• Cygwin : i would have to recompile Ubuntu. Ubuntu would run under Win7.
• Hypervisor based install (xen, kvm, vmware vSphere). This is the option i'm most interested in. Xen claims for up to 95% native speed. However i have no experience with this sort of virtualization. Xen is currently my favorite as it's open source (unlike vSphere) and kvm looks like a strange beast running inside the linux kernell (i would guess it has lower speed but i may be wrong).

Now, can someone tell me

1. Is it possible to re-use an existing install of Win7 under Xen. If so, do i need it on a separate physical disc, or is a partitionned disc OK?
2. If Win7 has it's own physical disc, is possible to use PCI passthrough to give direct access to this disc or is PCI passthrough limited to PCI cards?
3. Is it possible to use GPU acceleration on Win without using VGA passthough? If i use VGA passthough i'll need a different graphic card for Ubuntu IIUC.
4. Is it possible to share disc partition between virtual machines like i do for dual-boot?
5. Is there a way to share the clipboard? Well, for this one i doubt it but i guess it would be theorically possible with some shared memory.
6. Also, did i miss some better options?