Need help picking the best direction for a multiple subsite site.

Hey all,

I am a drupal yellow belt and have set up dozens of sights so I definitely have the basics down. I have also run multi-site single codebase sites but have not delved into the "shared" functionality that I have seen some people doing (I recently ran across this while searching for a solution to this problem).

I am using Drupal 6.13 and need to setup a site (fitness center) that currently has several locations but may potentially become dozens or hundreds of locations. Problem- I want the main site to have core corporate information with the ability to choose the location. The caveat is that each location is a mini-site within the main site with its own info, pictures, hours, staff, etc. I also need it to contain information that is passed down from the corporate site (perhaps in a block or as the main header for the site. You can take a look at http://www.snapfitness.com/ which is a similar layout (I don't think they used a CMS though, it looks hardcoded). Go ahead and put a zip code in and see how the top section stays corporate but the bottom section now takes on the the subsite theme. This is basically what I am looking at.

The organic groups sounds like it is a valid path but having never used it, I am not sure. Anyone out there set something like this up using OG? Any tips?

I have also heard that a multi-site with singe database, shared user base might be able to work also with feedapi and similar modules. Any thoughts?

I am ready to head down the OG path but since views and CCK are not my forte, I was hoping to get some insight before I start the OG learning curve, which I understand is quite steep.

Any thoughts?

Thanks in advance.

Rik