Ok need someone with more knowledge than myself to confirm my math here please.

1. 4ch amp rated at
60rms x4 @4ohms
90rms x4 @2ohms

Rear speakers
60rms 4ohm

Front speakers
40rms 4ohm

So plan is single sub running off Channel 3 & 4 bridged
Ch1 & 2 running 4 speakers in parallel
Each channel 4ohm + 4ohm in parallel =2ohm but each would get half the output so 45rms to each speaker does that sound correct?

Rears will run a minimum of 30rms so thier good but fronts would be 40rms rated but receiving 45rms.

The other option is just to wire the rears onto the amp 60rms speakers matched to 60rms amp... Would this be better considering the rears are 6.5" and the fronts are only 4" (run the 4s off the deck on a high pass filter)

I should add this is a budget install using bits I already have eventually I will likely run a 4ch just for speakers and a mono block for the subs but I'd redo the whole system with better gear