I did in my X just what you are explaining. I have Focal components in the front running off of the front channels of the 4 channel amp. The rear channels of the amp I bridged for the JL8w3 I put in the factory sub location (I had to modify the box a little to make it fit). The other 6x9 is powered from the factory amp. It sounds fine. I don't even hear the rear 6x9, that's for the people in the back seat anyway. I chose not to parallel the front channels of the amp because in my experience you loose sound quality not to mention the ability to fade (I would much rather hear the Focals in the front more than the 6x9). Just my $.02