i wouldnt even put 60 rms to the 4" they dont like it and hitting 100 hz with that speaker in a factory spot is near impossible, just get really good 6.5's and be done with it. its hard for a decent 5.25" to hit 100hz reliably but for a 6.5 its easy they will do that free air even.
i have my 5.25 quart components x-ed at 100 hz on 85 watts rms and they pound clean and clear but i use dynamat and mdf spacers as well.