VMware essentials vs essentials plus

[Fudgitsu4854]

Small biz owner, trying to virtualize our servers. Unsure which level of VMware to buy..

I came across this post. Is there any more to it than this?

 

[ADB100]

How many physical ESXi hosts? Do you need vCenter to manage it all in one place and the ability to vMotion VMs between ESXi boxes?
Might be able to do this completely free with ESXi(apart from the hardware obviously)

Proxmox.... Or something similar?