Ubercart 2.x

In trying to set up a Drupal 6.x Ubercart 2.x online store, I am running into a frustrating issue in that it is nearly impossible to set up a filter, exposed to the user, to filter by a taxonomic term. For example, I have an Electrical Circular Saw category that is located here:

Power Tools
- Electric Power Tools
- Electric Saws
- Electric Circular Saws

To this point, everything works as expected.

Now I want to be able to filter by brand:
- DeWalt
- Bosch
- Skil