I believe the 05 Sedan actually has an 8" sub mounted on the rear deck, but you will want to double check with someone that may have actually dug into that further. I am looking at possibly pulling that 8" out and replacing it if I can find more information on it first. It would be a whole lot better than the 6x9 option IMO.

One other thing I would strongly consider would be an aftermarket amp. If you are going to go through the process of upgrading speakers an amp will be very beneficial to you. Just my .02...

 

Thanks audiphile. I will look into getting an amp. Any recommendations?

 

I am by no means well-versed in all of the car audio brands being mostly a home audio buff, but I have been very pleased with the JL Audio and Alpine amps that I have owned in the past. I just bought an Orion XTR 375 and I am certain will post a review after I complete that install. There are many brands out there that are good, but first set a budget and look for something with the best SQ within that price range. If you are looking at doing both your front and rear speakers plus a sub, you will likely want to look at a 4 ch amp for the speakers and a mono to run the sub. (although IMO you really could just replace the front speakers and add a sub and be more happy with the soundstaging with that setup) You may want to take a look at Elemental Designs (www.elementaldesigns.com) as these seem to be pretty good for both their speakers and amps. (MB Quart, Phoenix Gold, Hifonics are other amps to consider) You could take a look around this forum as there are many other owners (currently including myself) who have upgraded their stereos and have found success with many various components. Best advice is to go to a good local shop and listen to what you personally prefer.