When you add more power, you improve your dynamic range and as an outcome you get better sound. If your volume sounds distorted at high volumes, or if you simply want your system to be louder, you may want to consider adding an amplifier for instantly clearer sounds at a larger range of volume levels that a amplifier inside a dash receiver cannot match. Overall, adding amplification will create a better sound quality and will provide the power to get the most out of your speakers and subs.
GoldenEar Triton Reference
Kenwood Excelon DVD AV Receiver w/ Navigation Only $799
Pioneer AVH-201BT DVD/CD A/V Receiver w/ Bluetooth ONLY 199.99
Denon AVR-X2400H AV Receiver w/ WIFI & Bluetooth Only $399
Kenwood CD Receiver w/ Bluetooth & USB Only $89.95
Kenwood Excelon CD Receiver w/ Bluetooth & USB Only 129.95
Rockford Power Series T1000-bdCP