My 07 Eddie Bauer came with the so called premium speakers. I'm planning to upgrade the stock speakers and hopefully get something that has a little more bass. I don't plan on installing an amp at this time, maybe later. I was looking at Kicker KS680's, which have pretty decent customer reviews, but some say they lack bass. What do you all suggest? Also, is there a difference in sound quality between 5x7 vs 6x8 speakers?