Okay, so my guess was right. Don't bother setting things up manually, qemu and libvirt are hellishly complex. If you don't need something super special, use virt-manager.

Just use the provided qemu image on the Kali site, import it, and you're good to go. Don't worry about the other stuff.

Depending in your screen you might have to set a custom screen resolution, but if you're using something standard, xfce should automatically recognize everything.

A little tip: set up an ssh server on the VM and upload an ssh key, that way you can get a Kali she'll quickly from the comfort of your hosts terminal.