I am gonna have 3 amplifiers in my trunk, and i only have one set of RCA preouts from my head unit. all the amps im getting have rca preouts too so i could wire a daisy chain, but will the signal be weaker and weaker the farther it goes down the line?
that depends on if the amplifier has a line driver or not.
personally I'd just use a 3-way crossover before the amplifiers to split the signal and set XO points and slopes as well as signal levels for each amplifier. one like the Audiocontrol 4XS or Coustic XM-3 or similar