Not sure exactly which parts of the bodybuilding site you're trying to replicate, but Wordpress has actually come some way as a CMS. In your case, I'd take a look at setting things up on an MU install, but you might be able to get to wher eyou need with custom post types as well.

Clicking on the SuperSite tab, that looks like nothing more than posts in different categories, though you could also have a separate post type for each thing. i.e. an exercises post type, a nutrition post type.

BodySpace looks like some kind of social network, which you could use BuddyPress for, I'm not crazy about bbPress, but it would provide a Forum, and as far as a shop goes there are numerous plugins for that - each with their pros and cons.

I haven't worked with Joomla in a while, but I'm sure there are similar extensions there. That said, I remember Joomla being more technically involved than Wordpress, so if the thought of MU + BuddyPress and the setup structure and other things scares you or seems over your head, consider working with a developer skilled in either of those to get set up.

And by all means, avoid anything that's custom. If you don't know exactly what you're going for you'll end up with a huge bill and more than likely subpar results that are tough to maintain or find help for. Wordpress and Joomla both at least come with a large community and lots of information available.

So the Windows/Linux determines which platform I can run? What if I wanted to integrate OSCommerce or Magento? Would that even be possible? Or would the store have to be on a separate part of the domain? Obviously some of this stuff is over my head. But I should have mentioned in my OP that I wanted to integrate Ecommerce in the site