i'm looking for a good nav systeem with i can direct use when i buyed the systeem. and it must have not only the highway's but also the US routes. like the US route 1.
i need also a little help on finding a nice cabrio car. i lookt allreaddy. but i can only find a ford mustang convertable.
Your 2 questions can be answered pretty simply: Everyone, and No one.
Every auto GPS system is going to have US highways and local roads on them. However, with all of them you are likely going to have to change the settings to "shortest route" and even that isn't going to always do what you want. That's exactly why every regular contributor here recommends GPS Navigation as a secondary option, paper maps will still be the best primary tool for deciding where you want to go.
As far as cars, i assume you are talking about finding Convertibles? In the rental car world there really are only two that are regularly used: The Mustang, and the Chrysler Sebring. The more important thing is that you will have very little control over which one you get. Every major rental car uses the term "or similar" in regards to their rental classes, and they do not guarantee specific models.