Advanced Car Classified Website

I am looking for an advanced classified car website.

It should have front end for search and viewing of cars which can be grouped by make etc back end where car dealers or private sellers can list their own vehicles through a subscription system. I would like something very proffessional looking and functional.

Please make an offer ONLY if you have designed something exact or similar that you will be prepared to share, as I do not want to waste time and want to move swiftly. Ideally a ready made package would suit me wonderfully and I can increase my budget depending on how good the script/package is.