The rear doors I used jbl power series 3 way 6x9s. Power series is no longer made but I think the gx series 6x9 is also same ohm. I tested the OEM speakers and if I remember right, all are 2.4 ohm, the jbl's(infinity also has same ohms if you get the 2ohm ones) the jbls I bought are exactly 2.4 ohm also. If you decide to do aftermarket subs and Amp, look for a Amp pro ch41, basically is plug and play. I went through a loc, better loc, a lc2i, (the locs and lc2i run off the OEM sub output, that output limits bass at certain freq/levels, never hit right bass notes and would lower bass as you turn up stereo) ax-dsp then the Amp pro(Amp pro has harness you plug into stereo and the harness from stereo, gives a clean signal and doesn't mess with bass, you just plug in, run wire from it to Amp turn on and run rca's) . Amp pro worked perfect, the ax-dsp worked great if you used a seperate knob to turn up bass because the app they have wouldn't lock on to the stock Amp and wouldn't let me select Ram truck with amplified system, plus customer service was zero help. Now I have a fiberglass custom box a member here sold me, 2 infinity 1200w (12 inch) subwoofers and a Soundqubed 1,500 watt rms Amp. Love how the setup sounds now. Highs are crisp and clean and bass is controlled and sounds great.