If you head unit is not a high end pure sound quality head unit like a pioneer 80 prs or kenwood 998x or some oldschool eclipse head units, you'll automatically have much better sound quality due to the processing power of the unit. You plug two RCAs from head unit to the output on the processor and get 8 channels of output. Can have midrange, midbass, tweeter and subwoofer all controlled separately or mid, tweeter, rear, subwoofer. You can choose whichever you want. Each channel you can have either high pass or low pass filter or both anywhere from 20hz to 20khz. There are 31 bands of graphical EQ for each channel for complete sound control. There's also time delay which makes magic happen by delaying the speakers closer to you so all the sound waves from each speaker reaches your ear at the same time. This envelops you in music and creates a whole soundstage like a full rock concert in front of you on the dash. Everything is easily tuneable with a software interface when you plug it in your laptop.