2 sets of components in convertible?

First off... Sorry if this has been asked before.  I've looked around and didn't really see what I was looking for (yet! haha)

I have a 2001 Mustang Cobra Convertible.  I also have a beater car, so I never drive this car unless it's nice enough to put the top down.  It has side exit exhaust and not very much in the muffler effectiveness department haha.  Basically it's a loud car.  To overpower my loud exhaust/engine sounds and I was planning on putting one set of 6.5" components in the stock door location and another set of 6.5" in the stock location on the side panels behind the front seats.  Everything will basically be pointed towards the centerline of the car (front tweeters will point at side mirrors on opposite side of car, front woofers will point at feet, rear tweeters&woofers will be pointed at each other in a location about a foot behind the front seats at shoulder level)

Is this a pretty dumb idea?  I really like the idea of sound being present both in front of & behind me. 

My planned speakers are to be MB Quart PCE-216 with a PA-1600 4-channel amp.

Any help guys?  Thanks!

Link to Speaker info:

Amp (it's actually a PS4-1600.  Sorry about misprint in earlier post):

http://mysimplecity.com/comersus/store/comersus_viewItem.asp?idProduct=124522

What are the cons with having a set of components in the front & rear?  Is price the only thing, or does it screw up the sound or dimension with too many speakers? Or will I hear too much sound coming from the rear tweeters?

I hate to ask simple questions, but I've never done anything with component speakers before & I really don't know what to expect.  I don't ever recall even hearing a set of components before.

The car came stock with tweeters & woofers in the door along with tweeters & woofers in the rear side panels behind the seats.  So it basically already has 2 sets of components, I just want to upgrade them.  

Thanks for any help guys!