So I bought a BOSS head unit for my 02 Pontiac sunfire and I have it turned up to max volume but it is like 1/4 of the sound coming out of my speakers. It is a 200w head unit and should have no problems that I know of to keep up with my 250w speakers. I tried to look through the owners manual as well as online to see what system I started with, had no luck. I was trying to see if I have a factory sub and undid a bunch of paneling to try and locate it as this was the only thing I could think of. My stereo looks like the Monsoon system with the cd player and all the other options(no cassette), but does not have the monsoon logo beneath the presets or when I turn on the unit. I went back and forth with the stock radio and the aftermarket and the stock still put out a bunch more sound. I couldn't find the wattage output for the original since I have no clue as to what it is. I saw a bunch of posts on locating the factory sub and the people looking never said where it was, just that they found it. I put new speakers in the front that are 4ohms but with the factory stereo they are still louder which makes me think thats not it. Is this a factory amp issue or is there something else that could be the problem?

Old post but was just checking in and saw no response. If you havent fixed it yet the new head unit will sometimes think you have an amp to power the speakers. There is a setting you can use to make it where it uses the internal amp. (Inside the head unit). Also did you connect the wires using the regular wires or the preamp output wires? They only send a bare audio signal so its barely enough to power the speakers. Also check the fader setting. Im about to put a touchscreen in mine and will be using a separate amp to power the rear speakers

I actually did, it was actually the module that was between the stock wire connections and the head unit. I think its called an audio bus, thanks for throwing that out there!