[SuperAkuma]

According to crutchfield.com your car accepts 5 1/4" or 6 1/2" speakers all the way around. As far as which speakers to get it all depend on how much you want to spend total and what you goal is. You already said you don't want anything crazy and just wanted "better" sound from your stock head unit.

If the speakers are all that you are changing out, I would recommend some nice coaxial speakers. Alpine type R are pretty decent so are the Pioneer D series coaxial speakers. These speakers will work well on your stock deck. If you plan to upgrade your deck, they will sound even better. After you upgrade your deck, the next step would be to add an amp to those speakers. Most average non audiophile will stop there. The next step you can upgrade your front speakers to a component set or add another amp and a sub depending on how much SQ you want.

If you should put a sub or not it all depends on you. A sub will greatly improve the overall sound quality of the system. You don't need to go crazy with the sub if you don't want to. You can get a small 8" or 10" sub and it will improve the SQ a lot.