How Preouts Work?

I found the the laptop put out 2v and the amp is set for that. Is that all that needs done? Im still confused. Is it the same type of output? It cant hurt the amps? In other words the way a head unit would supply the amp is the same as the laptop will?

It won't hurt your amps.  Set the gain the same way you would with any other source.  Do not trust the markings on the amp.  The easiest way to do it is to download a test tone to your laptop.  Connect it to your system.  Get some hearing protection.  Turn the amp gain all the way down.  Play the test tone and increase the volume until you hear distortion.  turn it back down just until it clears.  This is your maximum volume setting and can never be exceeded (this is where the sound card clips.)  Turn the gain on the amp up slowly until the distortion comes back.  Turn it back down until it clears.  Leave it there.  Now turn the volume on the computer back down to your normal listening level and you're done.

Thanks for the help! On another note now that its all working great. The amp im using is a 200 watts RMS, bridged. When the bass hits its taking a bite out of my trucks power. Any ideas. Is this normal for a amp this small? I took the amp from my brother and was thinking it might have been shorted out. I have a 105 AMP Alternator.

Things you can try:  upgrade OEM ground wire from battery to chassis, clean and wire brush connections, turn the amp's gain down a bit...

listen to Chopin....