I just wired in my EQX today and it made a big difference. The EQX is a pre-amp/line driver plus a 13 band parametric EQ. My Alpine IVA 505 only has 2 volt pre-outs so the EQS raises the pre-out voltage to 9.5 volts rms. I set my gains just a hair above fully closed and its very loud.
On the subwoofer side I was able to tame down the midbass peaks from my sub so now its very smooth and deep.
On the fronts was were it really shined. I have much more midbass from my fronts so I hardly need to fad my sub. The focal K2P's really have a lot of punch and even with my sub off I can feel the bass in my chest. With all this extra juice going into the amp, my amp doesent have to work very hard and I have no noise or hiss at all. It fit perfectly next to my amp.
I highly recommend this tool
AudioControl EQS Trunk-mount 6-channel equalizer and line driver at Crutchfield Signature