override template hierarchy

I’m trying to figure out how to override the order of the template hierarchy. So, I’m trying to go to a link something like:

http://www.domain.com/wordepress/?cat=1&p=11

I care about the category id more than the post id. Basically I’ve got 2 different categories, and I want to display their posts differently. So, for category 1 I’d use template category-1.php and category-2.php for the other category.

But right now its going directly to the single.php page (ignoring the category id).

Anyone know how to do this? Maybe I’m just thinking about this all wrong.

thanks,
bebeth