First off your aftermarket HU is NOT giving 50watts to your speakers, hence they are being drowned out by your subs. If you take off your back speakers you will just have the same amount of power(which is roughly 15-17 watts RMS) going to your front speakers. You cannot bridge the HU amp output to get more juice, either turn down your subwoofer or you'll haveto invest in a 4 channel (or 2 channel if you only want your front stage) amplifier.