hi, i just installed two infinity kappa speakers in front and 2 in back, and a alpine 9815. i got everything installed at circuit city. at first everything worked for couple min, then the speakers would go quiet,and i'd have to turn off/on and they would work again for couple min. now it only works for few seconds, and the speakers won't work anymore, but the head unit stays on. the guy at circuit said "the internal amp is prbly fried, get a new one"....and i do not have another 400$ to spend, so please let me know what the problem is and can i fix it. thank you.