I agree with the Panasonic suggestion. That h/u has a digital Tripath amp built in. Great choice for not wanting to get an amp. Not so sure your factory wiring will take it, but being factory amplified, it might be able to take it. As for upgrading speakers, it depends on how much you want to spend, and what kind of sound you are looking for. If you want a decent set of cheap 6x8's, get ahold of some Powerbass Black series. They sound damn good for only being 35 bucks a pair, at least that is what I can get them for. If you want something better than that, get a set of Kenwood eXcelon's. They have impressive sound for a 6x8, and are quite sensitive, making more of a lower power h/u than most other 6x8's. If you want to get components, but don't want to make a mounting ring, get a set of Infinity Reference 6802cs. Those are what I have, and they sound good off of my Premier P-300, and don't cost a whole lot on ebay, can be had for less than 100 bucks a pair. Mount the woofer in the standard opening, and mount the tweeter with double sided tape on the A-pillar facing in towards the center arm rest area. I haven't found a fault with the sound from them so far, they provide clean and decent sound for the money I paid for them (60 bucks including shipping). There are other options, just depends on what you want out of it.
