Okay, so my girlfriend has a 2007 chevy cobalt. She wants to get some work done to it and I am fairly electrical savvy but by far no expert. She wants me to do her speakers which I have no problems with. She wants to add some power to them though because she likes her music a bit louder and has no interest in a sub. So she thought up getting an Amp. Long story short, I have the basics on how to set up an Amp but I have two problems that I can't figure out how to fix. If you can help, thanks.

First: The head unit is stock and staying stock, so how can I go around that? My initial thought was running the head unit speaker wires into the amp directly and then the amp to the two speakers she wants to power. I figure that should boost it? Also it dodges my need for an RCA. My fear though is there will be lost power along the way or I simply can't do it that way.

Second: What does everyone recommend hooking the line to start the amp up to? So far i've heard things like ignition but i'd rather not, i'm thinking the cigarette lighter but so far i've heard you should use a 1 amp fuse for safety. Wanted any thoughts or opinions on this & how to set up the 1 amp fuse, since I don't really know that much detail. I'm sure I could look it up but I find it easier to just ask

Again, thanks in advance!