@olivierlambert That is wonderful news. We actually will be closer to a 1.2:1 or 1.1:1 ratio of vCPU's per physical core - our hosts are old beasts, but we don't work them hard. We had some 10 or 12 VMs on one while it was running VMware (DURING our migration, so a it was running more than it normally did) and it was consuming maaaaaaybe 30% of the available CPU power. There really aren't that many of us.
We are probably not going to purchase XCP-ng Pro Support, but we absolutely WILL be purchasing a Xen Orchestra subscription at the Starter tier. I think it hits all the features we need, it gives us a real support contract for our virtualization solution, and it is our great honor to support an open-source project!
Thanks for answering my question. Hopefully it's helpful in answering someone else's out there on the internet.