This will need to be field-tested, while it can sound the speaker that does not mean the performance is stable if you turn up high volume or play for long time. It may cause another potential sound distortion problem. I have just installed my old amp just to drive for my midbass speaker dedicatedly that is rated 120w @2 ohm due to my other amp just can drive the speaker with enough power due to it is never rated to run on 2 ohm. The difference on the sound result is significant.most of the newer head unit can handle effectively 2 ohm front and 4 ohm back. In fact, if you have premium or higher with 6 speakers, it is effectively 2 ohm front channel.
I would suggest you put the sound deadening mat on the outer door panel through the speaker hole. Just a 6x6 will quiet down the outside noise a lot.