I spend A LOT of time in my truck, usually 2 hours or more a day going from work and back. The stock HU just wasn't cutting the mustard, either in volume or quality, so an upgrade was in order.
I went with an Alpine INA-W900BT HU. Killer unit, easy to use, navigate, not too distracting going down the road. The Alpine OEM GPS is iffy at times. It will get you to where you are going, but it may reroute you around a road it sees as "Unverified." This thread has a lot of pics and is a great write up on the Alpine. It was a great help to me when choosing a new HU.
Once you get the new HU installed, the stock speakers can cut loose a bit, the speakers are actually better than what the stock HU lets them be. I ran with the Alpine HU and the stock speakers for about two months and it wasn't awful, but it still wasn't what I wanted.
At this point I must confess I am a complete music nerd, with a wide range of stuff on my MP3 player. I wanted quality sound no matter what I put through the system, be it Beethoven or Slipknot. So I went for the whole system and got new speakers, amp, subs, the whole shebang.
I went with the Alpine Type X Pro for the highs and mid range sound.
For an amplifier, got the JL Audio XD700/5.
For the low end punch, a JL Stealthbox with a pair of 10" subs in a sealed box, with a knob in one of the knockouts to dial in just how much bass I want.
Finally, to tie it all together, an Alpine Imprint processor. This thing will time the music so it all reaches your ears at the same time.
I'm really happy with this set up. There is just enough bass to push on your back playing at a normal volume, there is definitely a threshold when the sub seems to get moving and add more than just additional punch.
The amp is under the driver's seat, with the Imprint under the passenger seat.
Just wanted to share this with y'all.