Cisco Communications Manager (CM) server sizing recommendations

I'm running into more frequent projects where I need to recommend new servers for Cisco IP Telephony deployments. Over time, I've found bits and pieces of this kind of information in a flood of documents, but cannot seem to find a "go to" reference for what seem like pretty simple questions.

Is there a table of recommendations out there for sizing an appropriate server for different flavors/versions of UC products?  I’m on top of how to determine if a particular, existing server is sufficient to handle a new version (or if RAM/HDD has to be upgraded to make it work), but what I can’t find (yet) is guidance on, for example:

- recommend an appropriate Cisco Media Convergence Server (MCS) for a Communications Manager (CM) 8.x environment with 600 IP phones; 1,500 phone...

- recommend an MCS server for a Unity Connection 8.x deployment requiring 400 voicemail boxes; 1,200 VM boxes

and so forth.

I'm not just looking for specific answers to the above, but links/references, and an explanation as to who to derive them in the future, no matter what the environment.

Thanks!