Installing an aftermarket sound system

jackhammers ? seriously? 300 lb paperweights.

im a SPL competitor wouldn't bother with anything Memphis but due to size of cab and how much junk most drivers carry with them. I would suggest 4 10"s medium level (not cheap not super expensive) subwoofers in a big truck. as for wiring amps with high level inputs that's another bad idea. it may get you thru but my motto if your going to do it , do it right. replace the factory head unit with a decent 5v-8v pre-out sub rca's and this will make all the difference in the world in your music. far as the mids/highs go replacing them with 2 ways will be fine (no real need for component sets or 3/4way speakers) if you amplify those you will be really getting into some jams while holding that wheel you may just have to do a break dance. capacitors would only be needed on the sub amp how to know when ? if you turn it up and drop some low notes and see lights flickering/dimming (like dashboard lights) its time for more batteries or Capacitors. also use a Mono block for the subwoofer amp not a 2 channel or 4 channel etc. make sure you use the appropriate gauge power AND ground for your current needs on amp. 1500 watts - 600 watts RMS power = 4ga more power? 0ga
Worst thing for any electronic is Heat/Cold/Wet And Voltage being out range so don't beat on stuff when your voltage is too low. one last thing my 00' pete had premium sound w/factory sub and it did pretty good after I replaced the HU only.