front speakers static/low sound

Ok, I'll try to explain this the best I can. I'm in process of changing my stereo system in my 91 Toyota 4x4. The previous system was an older pioneer cd, fosgate 4.5" in the front, stock in the rear, kicker amp off the rear rca w/ 2 kicker 10" truck boxes. It worked fine but I never got much sound out of the front speakers. I thought that maybe the decks amp was going bad or? So my new system includes a fosgate cd/mp3 player, new wires directly from the deck to the front fosgate 4.5", the rear rca running to the same kicker amp with infinity 3way 6x9's, the sub rca running to a mtx amp with a jl audio 10" sub. I hooked up everything without hooking up the speaker wires from the 6x9's to the kicker amp, but the amp still had power to it. The front fosgate speakers running off the deck worked fine. Then I hooked up the speaker wires from the 6x9's to the kicker amp and they worked fine, but now not much sound coming from the front fosgate speakers??!! There is also some static coming from the 6x9's and the front fosgates. The only difference was hooking up the speaker wires off the amp. Any clues? I'm guessing it has something to do with the amp since that is the only common component in the 2 systmes.