As far as virtualization is concerned what you are looking for a Type 1 Client Hypervisor and even though I understand what you mean about running two hosts "side by side" that isn't how these things work. Either you have a Hypervisor that takes control of the hardware and it boots VM's or you have hardware that can actually be physically partitioned, effectively presenting multiple systems that share common IO\console hardware. There are some examples of the latter out there but they generally have a low powered rapid boot\appliance style system combined with a full blown system for more serious work (e.g. this DFI Hybrid) so I don't think they would meet your needs either.
With any virtualization type solution your operating systems will always be running as Virtual Machine Guests and they will see virtualized hardware. If performance is what you really need, especially at the network level, then either move to a proper bare metal server Hypervisor like ESXi\Xen and accept the limitations of running your desktops from a remote system or stick to a bare metal OS install if you need to work at the hardware level.
As Zoredache has said Citrix Xenclient now have a Type 1 Client Hypervisor but there are very stringent hardware requirements. Your operating systems are still classed as VM guests and see virtual, not physical, hardware although there may be some form of hardware IO virtualization going on too that might come into play. Given the very strict hardware restrictions it seems likely that hardware IO virtualization is key part of this so wider hardware support may be very slow to appear although if that is the case then performance of the VM's should be very close to bare metal.
There is a good article on the state of play in the market for client Hypervisors as of a couple of months ago by Brian Madden in this . There are some other smaller players in the market, Virtual Computer's NxTop for example, but there are no end user type products (like VirtualBox\Workstation\Parallels) as far as I'm aware.