Just wondering how hard it would be to make the 4" cutout in the rear deck big enough to fit 5.25s or 6.5s.....I plan on replacing all speakers and running a 2 channel for the fronts and a four channel to the rears.The problem is I want to pump like 150 rms to the 6x9s but my 4s are rated at 50 rms....open to suggestions, thanks.