If I buy a 2-channel 100 watt amp and hook it up to my 2 front speakers and 2 back speakers will each speaker get 100 watts. Or do I need to get a 4 channel to do this.

 

you answered your own question. thats 100 wattsx2 channels. a 4 channel would be the best route since then you dont need an amp thats 2 ohm stable.

 

Well my friend just offered me a 400 watt amp for free should i take it and hook them up to it. Or would I be safer getting a 4 channel

 

deff. depends on what the rms wattage is on the amp, and i wouldn't advise an amp to your stock speakers, you could

but it would deffinantly be more than what they could hold, replace them before you run an amp to them

 

I have replaced them but im not sure if the 400 watt amp will be too much for them to handle.

 

specs? links? channels?

its not power that blows speakers/subs