Hi,
If you are running separate NAS based storage for running your vms, then a normal B85 based motherboard that supports 32Gb of memory is more than sufficient. z87 based mptherboards are only required when you are overclocking for gaming purpose or need more sata poarts to connect more hard drives. even in that case those ports will not be of much use unless you pass the drives through vt-d to a nas vm running from the hypervisor you will be running on this board. Unfortunetly asus is not much friendly with vt-d passthrough. So you can't acheive that. Genrally "k" type processors are overclocking friendly and not virtualization friendly. intel 4770 will never be a overkill untill you are planning to run less than 4 or 5 vms, however the 4770k and the z87 motherboard is looking like a overkill to me.