You are going to run Focal components off a factory amp? Really?

You would be much better off running a little less expensive components and throwing them on a 75x2 amp, or if you are upgrading the rears, add components there and a 4x75...

The WORST single thing you can do, especially to nice speakers, is to underpower them.

My $0.02

 

Ok here will be the set-up:

Amp = Infinity Reference 5350a High Performance 5-Channel Amplifier
Sub = SSA DCON 12" sub in ported box (removable for when space is needed)
Fronts = Focal Access 165A1 SG
Rears = Still undecided on this one as there is only 50rmsx2 so no kicker subs there. Maybe just leave factory or put in another Focal componet set

That sould about wrap this project up.

 

Should sound very good, you will probably need at least a single farad capacitor so you do not have the dimming of the lights when the amp draws big power, but it is cheap. It is harder to find a place to mount the thing than purchase it.

I would HGHLY recommend another set of components in the factory rear spot, with custom mounted tweets for imaging. That 12" is going to be a lot louder in that car than you think...

I have never used the OEM amp, but it must have a crossover in it to control the factory subs, you will lose that when you remove it, so unless your new amp has an independent X-over for each channel, you will need an inline X-over if you do not replace the factory subs...