Perhaps a picture would explain what I'm trying to achieve better than words will, but I'll try with both anyway.
http://files.headsonic.com/files/1/layout01.gif

On the main index of the site I want the two categories (Headphones and Microphones) displayed as images directly below the logo, and for the main page to be on the headphone category by default. When one of these two main categories is selected, the pink bracket appears next to it.

Below this, I'm looking to the these 3 subcategory boxes to appear, with each one displaying the complete selection from the catalog that accords to the particular criteria selected. For instance, if you hit $0-50, you would get every single model of headphone in the catalog that is between $0 and $50.

I'm happy to do this catalog arranging myself by hand for each product in the backend (putting each product into 3 subcategories perhaps, given that each product will have a price, type and brand attribute), but I have no idea how I would go about beginning to work with this.

Thanks in advance!