You need Enterprise Plus, although there's still a kit if 6 CPUs and 1 vCenter Standard will do you.
I have no idea if there's an "upgrade" SKU from your current kit.
Thanks for your response. So I can either upgrade vSphere to Enterprise plus OR I can upgrade my vSphere Essentials kit to a vSphere Acceleration Enterprise Plus kit? If this is the case what would be the most economical?
I would guess at the Acceleration Kit, but honestly don't know.