Go to stereo shop....listen to all the different speakers till you find ones you like. TAKE YOUR OWN MUSIC CD and listen to what you like!
Once you find a set of speakers...install those in the doors, Try that with the factory head unit for a while. If still not enough, then go head unit shopping. Pay close attention to how the controls work, would it be fumbly in the dark? Rotary volume is generally the best...button up/down for volume sucks, I like to reach over zip that knob up or down as needed myself. Also pay particular attention to the level of brightness and colour of the display. Some head units have different colour options and can be adjusted up/down in intensity as well. My wife bought a unit that is BLUE and I mean really really bright BRIGHT BLUE at night so much so I have to turn the unit off completely. Or stick a big tab of tape over the display because it is just overwhelmingly bright. It has a negative effect on my night vision and is distracting!
Once you find a head unit with features/display/controls you like. Invest in a factory harness adapter. This allows you to sit in your easy chair, wire the stereo to the adapter, go out to truck plug in and slide deck in ....barring that you already installed the sleeve for mounting deck!
Take a piece of cardboard, label it stereo removal tools, stick the tools that come with the deck on the cardboard and hide that some place you know in your cab! A failure on the road and no way to remove stereo sucks....trust me on this!
There that's my how to make it louder better...There is more but it requires some cutting of wood to fit doors and small amp etc. How fast do you want yer IDI how much do u wanna spend....HOW LOUD do u wanna go...how much do u wanna spend!