As everyone else says, you need a HU in order to unlock your sound potential. I myself need quality sound in my life, my set up has lasted me 3 years and still is the best thing I've heard and everyone else who's heard it agrees. And all I have is a sub and upgraded HU running on standard speakers. Sounds simple but yet they're expensive!
Running a chavtastic Vibe black air 10" sub and amp combo taking up half my boot space which is connected to the highly recommended but yet expensive "Parrot Asteroid"
Too much stuff to list but it's;
Handsfree phone etc
Voice recognition mics (press the speak button to call or choose an artist to play)
Subwoofer input
Detachable face
Bluetooth
Line in AUX
SD Card
2x USB port
1x USB dedicated to Apple products (grace note media database, basically portable iTunes)
AM&FM Radio
GPS/Satnav
Couple of Apps
Plus Quite a few more I've missed and a truck load of custom settings to tweak!
Here's a few photos of said unit and a few options I've just mentioned:
Here's the mini iTunes I was on about. If using the apple usb you get options to see your album artwork etc, use the voice recognition search to just say a artist or album name, it'll search said Apple product and play
Here's a few shots and settings:
Option with or without the album cover:
With the apple usb you can connect and charge your phone (if Apple) it uses your stored music as above. In my case I use a in car usb in the cig lighter to charge the phone and I've hid my apple wire as so down and around under the Gaitor plastic connected to an old unused iPod i had lying around. It charges when the cars on and boots up when the cars on so Music is always there. Like so:
Detachable face just incase you're paranoid about theft. SD card slot behind it
More settings;
Anyway that's that. Don't look like a gameboy or Christmas tree, tons of settings for your toons and different ways to blast your tunes in the retail parks or race wars.
Tad expensive but then again how much are people willing to pay for uprated speakers and tweeters?
Enjoy my long ass winded post that took me a while to write up.