You can have a quick browse at virt-manager, just as an aside as to whats also there.. you never know, you might even like it..I think having such a tool can give you a bigger kick in performance and less disk defrag issues.
You would have to go for a steep learning curve and the conversion time to make it all work perhaps.
If updates is your main time spender, try WSUS, nothing related to VMs itself, but it helps with deploying windows updates.
Lastly, check Hanselman's blog on Invirtus, Virtual Machine Optimization at its best.