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Usually if your site is using a dynamic code, than the Url for a category of black colour cars having Audi model, will generate like
http://www.somesite.com/index.php?cPath=32&osCsid=1c2a1fb557c5b04
http://www.somesite.com/itemcat.asp?cid=product%20category
So its recommended to use url like
http://www.somesite.com/black-colour-car/audi-2008-version.html
http://www.somesite.com/black-colour-car/audi-2008-version.asp
http://www.somesite.com/black-colour-car/audi-2008-version.php
Changing dynamic URL's in static ones is easily possible by Url redirecting scripts and server side changes. Your developer can make it easily or you can find out help, on internet easily.
Now the most important things, as you have decided keywords ,you should keep your filenames as your keywords are. It helps the search engine crawlers to keep the track of your page easily and becomes very much useful for indexing. This way simply promotes your website keywords.