Exchange 2010 Best Practices - Database Purposing/Design

Greetings,

We are going to be transitioning from a single Exchange 2003 Standard (physical) to a single Exchange 2010 Standard (on VMware).  As such, we get 5 DBs.  I'm looking to see what peeps have identified as best practices for designs, as I don't really concur with what is being proposed in our department and I want to see what the experts have to say.

We have 500 users/mailboxes.  We use Public Folders.  We will be using Archiving (and finally get rid of PSTs).  We're tentatively looking at 2GB mailboxes and 10GB Archive mailboxes (though only 10% of our users will use that volume).

I would think that you'd have 1 DB dedicated to user mailboxes, 1DB dedicated to Public Folders, and 1-2 DBs dedicated to Archive mailboxes, with a 3rd available as needed.

The proposed department solution is to have a user's primary and Archive mailbox on the same DB and balance the, across 4 DBs, with 1 DB still dedicated to Public Folders.  This seems like a nightmare to administer and inefficient use of the DBs.  

That said, I haven't used anything but Exchange 2003 for 10 years and have only read about Exchange 2010/2013.  I've looked into Exchange 2010/2013 Best Practices documents, and they are good about resources (CPU, memory, drive space, logging, etc), but I've been unable to find a clear design recommendation for database usage/allocation.

I appreciate any advice you experts can provide.

Thank you,

Jeremy

Oh, one other thing that is unrelated to the DBs, but may impact the project.  Our AD function level is 2003.  We will be raising it to 2008 (not R2) shortly.  Is there any benefit or impact to raising the functionality level before or after the implementation of Exchange 2010?

Thanks again.