Hey there. This is my first post. I have been reading here for a bit though.

Anyhow, I really don't know much about how the high quality sound equipment in cars works. I am wanting to upgrade the speakers in my current car. A 1992 Toyota Corolla Sedan DX. According to the Xpload website, it has 4" speakers in the front dash and 6 3/4" in back. However I'm not sure. The car has a... I think 100w Pioneer Head Unit and has Infinity speakers in square boxes on the back of the rear seats. (The peice of carpeted space below the rear windshield) Anyhow I don't know if this car was upgraded by its past owner or not. The reason I don't think so is because I've seen many many of these same Toyota Corollas with identical boxes and Infinity speakers which leads me to beleive it was most likely a factory upgrade? Maybe a upgraded sound package? Anyhow I'm interested in upgrading these speakers since they really aren't to kind on the ears... lol... They sound kind of crummy. I would also be interested in adding a Sub somewhere in the car. I don't want to win any dB competitions and a I CERTAINLY don't want any extra police attention lol, so I'd like to maybe sound proof it a bit and just get some nice bass to make my music sound better.

Anyhow I don't really know that much about how to hook it up, but I'd assume its just swapping out the speakers if you get the same size speakers. I haven't the slightest about the Sub however. From what I read is it correct that you need to buy an Amp? How would the set up go?

Head to Front Speakers
Head to Rear Speakers
Head to Amp
Amp to Subwoofer

Is that correct?

Anyhow those are just a few questions I've had after researching this for a bit. Any input is appreciated, I'm just trying to learn as much as I can.