Poseur

As I said before, I really honestly think you'd be better off to just buy a mid-line set of components that has a crossover, that way you'll have something to block out the highs, (if you buy them seperate it'd likely cost the same or more) and just set the tweeters aside, or try them up front and see if you like them better than whatever else you've got, bare minimum you've got an extra set if you happen to toast any. As far as speaker fit in the the rear, if you take the door panel off you'll see the ring that protrudes back to the speaker-face. on the stock speakers it pushes into a foam surround kind of thing, but on bigger speakers it WILL hit the rubber surround. if you can, it'd be best to just take your door panel and "test-fit" some different speakers up against it if this is at all an option. Matter of fact, I've got a friend at a shop, and I've got my door panels off, and I need to go get my kappa 5x7's looked at, give me a couple days and I'll go try a couple different brands. They carry infinity, Eclipse, sony, kenwood, MBquart, and a couple others, I'll see what I can do. The surround that close to the door panel's kinda had me uncomfortable for awhile