I noticed that both 'linux-image-xen-amd64' and 'linux-image-2.6-xen-amd64' are missing
Sorry to bring up this old thread. I found a proper answer to this problem.
linux-image-xen-amd64 package does not exist in Debian Wheezy, because the default kernel (linux-image-3.2.0-4-amd64) supports xen.Or in another word, "This kernel also runs on a Xen hypervisor. It supports both privileged (dom0) and unprivileged (domU) operation." (https://packages.debian.org/wheezy/linux-image-3.2.0-4-amd64)
I clean installed the new released OMV 2.1.7 stone burner yesterday in my Xen hypervisor. The OMV vm boots as pv out of box.