In addition to the CPU licenses you may also need to "vCenter Server Standard" license to manage the hosts in a cluster! If this is the first time you purchase vSphere licenses you may take a look at the "Acceleration Kits" which might save you some money. Standard, Enterprise and Enterprise Plus Acceleration Kist include vCenter Server as well as 6 CPU licenses, so you will have to purchase two additional CPU licenses to cover your hosts. (see http://www.vmware.com/ca/en/products/datacenter-virtualization/vsphere/compare-kits.html)
André