New Speakers - Polk DB6501?

RedShifter

Hi,

So Im looking to install some door speakers. Now from what I have read I am going to go with a set of component speakers rather than coaxial because it will sound better. (In about a month I will put a sub in the back too)

Everyone seems to rave about the Polk DB6501

Amazon.com : Polk Audio DB6501 6.5-Inch 2-Way Component System (Pair, Silver) : Component Vehicle Speaker Systems : Car Electronics

What do you guys think? In the description it says it comes with adapter rings. Will this be sufficient or do I need to head over to Zenclosure to purchase their spacers?

I have also read that I need to run new speaker wire? Why is that? Why cant I just remove the old speaker in the door and use the existing wires for my new speaker? And does this rule apply for the tweeters too?