Hello there,
I would first like to start by asking you, what's The year, make, and model of your car.
2. You really should add an amplifier, it will allow you listen to your music alot louder with no distortion if set properly. Virtually every high power headunit only outputs about 15-25 watts/RMS. Reasonably priced amplifiers are rated between 50-75 watts/RMS. Match the amplifier to the RMS rating of speakers you are using.
3. I highly recommend upgrading your speakers, the 1672R's are not good for sound quality. Consider getting component speakers for the front doors, much better