New update.... veeam just release the veeam backup free version which does most of the backups you probably need for vmware, without support for replicas, I don't know if its supported for the free ESXI version.
Few points:
1. Dual CPU or Single - Consider also that veeam license is per CPU, and from what you wrote you will run, one cpu can handle it pretty fine, usually the problem is memory for those kind of VMs, I never encountered CPU problems with todays hardware.
2. Without going into too much...
my first post, but no newbi (I hope :) )
This is a very standard setup, except what I do with it.....
I bought it a year ago when my KVM server was dying (unfortunatlly it actually died a week after i got this one and before I managed to migrate...)
I did plenty of research before purchasing...