Hosting with Cloudmin/Virtualmin/Webmin

I'm trying to wrap my brain around the question of implementing hosting services with Cloudmin, Virtualmin, and Webmin. Basically, I'm trying to figure out a migration from HSphere to something else (since it seems that Parallels is incapable of maintaining either HSphere or Plesk these days).

What I want is a platform that will leverage servers as black boxes ultimately and that has led me to Cloudmin and the possibility of deploying a cloud. The goals are to setup a test cloud as a proof of concept at first. Initially, only virtual servers would be offered (that is, traditional virtual web servers managed by Virtualmin). What we have now is an HSphere cluster deployed across 10 servers (web, mail, dns, etc. are all distributed). Therefore, I'm looking to first setup a system that will just replace what we have now and then eventually migrate to virtualization for flexibility, etc.

I've been digesting whatever documentation I can find here. Installed a VM on my notebook to get a better idea of how Virtualmin and Webmin are related (since I had suspected that the online demo was fairly locked down and, hence, didn't provide the whole picture). The conclusion I have reached is this: Webmin runs on all managed servers and is the control panel (of sorts) for the box owner...it's a layer of management to which there is no comparison really in cPanel, Plesk, HSphere, LXAdmin, etc., because all of those platforms integrate everything into what we could compare with Virtualmin. Is this correct?

So that means in a hosting service environment customers would be granted access to a Virtualmin account in order to manage their resources, similar to how an account is created for a customer in cPanel (or whatever). And then Usermin, could be offered to let a customer's end users change their password (or check their mail without using another client).

Now, in looking at Virtualmin, I see the "Cluster" management area in the menu tree. Is the idea that you would deploy Virtualmin on a single master server, Webmin on all nodes, and then configure/control the lot of nodes from the single Virtualmin server? Or do you deploy Virtualmin on all servers but then you can configure one master from which you would control the whole lot? This is my first point of confusion (I think). I mean, doesn't Virtualmin have to be configured on ALL servers where you are configuring customer accounts? In HSphere, everyone logs into the single control panel and everything is managed by the single control panel so that's probably why I'm finding this setup a bit foreign. Obivously, in Plesk (without Plesk Expand) or cPanel customers login to the single server that hosts ALL of their services.

My interpretation is that Cloudmin kindof implements what the HSphere control panel does (a single place to manage all physical and logical servers and accounts) but takes it a step further with virtualization support. Is this right?

Keep in mind that I will be building this entire setup from scratch. Ideally, I would like one control panel from which to manage all systems. I would also like the ability to seamlessly introduce virtualization down the road with as much ease as possible. I'm thinking that Cloudmin will help me accomplish all of my goals except for one: the distribution of services across hardware (that is, centralized mail, dns, db, to service all of the web hosts), which is the current HSphere setup--but I think (!) that even this can be accomplished with server templates (or is account templates?).

Fianlly, how does WHMCS (billing) fit in for this setup? Do we configure the Cloudmin module on it or the Virtualmin Pro module? Perhaps the cloudmin module replaces the virtualmin module?