declare categories in subforums?

[jl255]

I want to have categories in my forums so that the subforums can be organised properly.

For example:

if my forum is an auto site, with the following forums:
mercedes
bmw
mazda

and inside bmw forums, i want to declare categories like:
models, modifications

and inside the 'models' category, i want to declare subforums like
3-series
5-series
6-series
but i want to display all these models subforums with last post, etc. just like how normal subforums will be displayed. unfortunately, when i declare them under a category (i.e models), it just shows as small subforum links under the category name instead of normal subforum display.

i'm hoping that categories will work just like how they do on my forum homepage, but when categories are declared inside forums, they act more like subforum declarations rather than categories in terms of display.

Is there anyway around this?