I have never seen confirmed that google prioritizes keywords as directories over keawords in file names.
If you want to dig a little deeper into SEO have a look at
http://www.googlerankings.com/ and find some interesting links at the bottom the page.
At http://googlerankings.com/seolinks.php you can find more ressources. Be sure to check out http://www.vaughns-1-pagers.com/internet/google-ranking-factors.htm too. Although it hasen't been updated in quite a while it still has valid information.
Good Luck!