The gear you suggest seems a bit much mate, unless the system I am suggesting is too low key? It will play loud, play clear, have plenty of bass etc, it will more than likely shake your rear view mirror and all that. You must remember its a ute cab, a tiny amount of space, your sub is 50cm away from you at very most, probably 30cm away not 3 metres like in a sedan.
Where would you mount 3 amps? I don't see that being needed at all, simple is usually better when it comes to audio mate. This system would sound good and not break the bank. If you want to spend more money, get better front speakers and a better amp. Also spend a tiny bit of money on RCA leads, maybe $30/run for Stinger Pro3 or Aerpro Crystal.