Oh come on guys, the stock head unit isn't that bad! After all, he did say that...."I was thinkg about adding a new amp to my stock stereo"......and not ....."I want to rip out my entire system and start over!"
Whitethunder:
Welcome to the board! Your stock head unit will be fine for a simple upgrade. Any shop should be able to do the work for you, it is an extremely simple install. Head to a CC or Best Buy, or your locally owned shop if you have a good quality one that you trust, and tell them that you would like to add an amp to your factory head unit.
You will most likely want to upgrade your speakers, especially your front set. This will make a dramatic difference in sound qualtiy and will certainly be worth the upgrade money. A shop will most likely want to sell you a component set for the front doors, which is absolutely of no positive benefit compared to a coaxial using the same woofer and tweeter. The 6.5" coax will save you some money was well.
As far as an amp is concerned, you'll have to decide what you are planning to upgrade.
1. You can buy a two channel amp and use it to power upgraded front speakers.
2. There is the 4 channel option next. You can upgrade the power to the front and rear speakers with a 4 channel model, or use the 3rd and 4th channel bridged later for a subwoofer while the front two channels run the fronts, letting the rears stay stock.
3. Five channel amp: Upgrade all four door's power and have a channel for a sub now or later.
Let us know what you decide on, and have fun!