Categories and Siloing

I think it really depends upon the category topics and the competitiveness of the keywords. In general, providing useful channels of content (ala a theme pyramid) should help you spread the PR around the site and help users get to the content they're looking for. It takes a bit of forethought - and a/b testing if you have time. Set up some tests to find out what silos might work for your topic and/or to try alternate methods of getting the user down into the content you're targeting.