Hi, I bought 4 HD speakers (250) watts each from wall mart, Probably 50 watts max. 1000 watts sub and 400 watt amp. Since stereo outputs only 15 watts rms x4, i tried running my back speakers through amp but the sound quality is bad. I have factory wiring for speakers, 8g red power wiring for amp and 18g wire running from amp to sub. Got any suggestions how i can improve sound quality. Will post the exact name of stereo later this week after i get back from work. Thank you.