The Right Speakers Make All the Difference to Quality of sound.
If you have already invested in a good quality head unit then having the right speakers is a must !
Use a 3 way (or 4 way) crossover.That way you are splitting the Bass, mid and treble. For a more clearer professional sound
A good Example of this would be a 12 inch subwoofer a pair of 6x9's and a pair of tweeters.