Well, I'd spend $200 just on the front components since you'd want to retain your component setup. And leave the factory 6x9's unless if they're blown. You don't want to take your component setup to a coaxial setup. You get worse sound imaging and your high's won't be as good as an aftermarket componet set. Go to www.groupbuycenter.com or go buy used speakers that were put on for like a month or less. But definitely DO NOT go from components to coaxials. So go get your fronts before your 6x9's in the rear. The stock 6x9's aren't too bad so I'd concentrate on getting the best front component set as possible.

P.S. Your front door woofers are 6.5" but I don't know how big your tweeters are. They're probably 1". So replace both!