Allocating 100MB to every site without it being shared

[fitzgeraldjw]

We are just getting our full Sharepoint Services rollout begun withing my company, and I have a question regarding site space allocations. We want to allocate 100MB to each departmental site, and are trying to figure out the best way to do this without having to increase the overall space on the virtual server, and have it shared amongst departments. I believe we can accomplish this by creating a new top level site off of a virtual server (Central Admin page, manage virtual, create top-level site) creating virtualserver/sites/sitename, and specifiying our template that is set to 100MB. I know that obviously if you go to the actual site and create a child site, it will share space, but what about the way I am describing? Any insight on the best way to go about doing this would be appreciated. Thanks in advanced