you'll be fine with the head unit power. The reason why component speakers require lots of power is b/c they're not as sensitive as coaxal speakers. The inf perfect you want has 90db sensitivity which is pretty good. Some component speakers have low sensitivity like 83 or 84db. That means it requires 4 times the power to produce the same loudness as those infinity perfect. If youre not sure about adding an amp, you can hook it up to the head unit. If it's not as loud as the original speakers then add an amp. Don't worry about the 2 ch amp over powering the inf speakers and drowning out the rear speakers. You can always adjust the gain on the amp to even out with the rear speakers.