the 9887 has a 5-band parametric EQ. it is plenty. IMO if you need more than that, your installation is not up to par. running the front components active will offer more benefit than buying a fancy EQ. passive crossovers are too generic to be of much use in most vehicles. the crossover point needs to be adjusted for the installation and speaker locations. i've corrected most of my issues with simple crossover point and slope adjustments.
i used to have an Alpine PXA-H701. with multiple 31-band EQ channels (basically per driver) i found myself using it too much instead of fixing the install. now that i've eliminated external processors and spent more time on the speaker install, i'm much happier, my soundstage is better, my tonality is better, and my RTA results are better. i'm never done, and after changing speakers i need to re-evaluate placement and crossover points. i seem to find improvements every day, and using an EQ is not one of my steps.
a basic EQ cannot fix phase interference because the filters aren't steep enough. trying to do so will result in very unnatural sound since you attenuate everything around the actual problem without eliminating the problem and it's harmonics. modern processors aren't good enough. for example, in 2002 when Geoff Martin helped Bang & Olufsen design their first OEM automotive sound system for a Audi A8, he needed 285 digital filters on 14 speakers (ref: IEEE Spectrum 02/2013). he basically attacked resonance issues by applying very sharp filters at the fundamental.
having an RTA at my disposal and hundreds of hours of time experimenting i've found that an EQ is not necessary if you choose the correct drivers for the intended location, and do what you can to turn that location into a proper speaker enclosure. these days, i use 2 of the 5 bands in the HU. one of the 2 is to fix a 125-140Hz resonance in the floor. the other is to compensate for my crossover point overlap.
when installing speakers in a car, you ARE the system designer. you control every aspect of the system. attack it as if you were building floor standing towers for your home. would you start with a hollow, reverberant shell of thin metal full of holes and put a thin plastic cover on it? nope. so our
#1 goal is making the airspace behave acoustically and structurally like a very rigid and well damped enclosure. my build log (and even the Scion tC) is an evolution, and doing it step-by-step allows for evaluation of each step. in the end, all of the steps (damping, stiffening, absorption, and seals) are required for good performance. if you knock on any part of the door and it still sounds like a car door, you're not done. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
the other major challenge is where we put speakers and where we sit. being off axis from speakers, having speakers aim at reflective surfaces (glass), and having the speakers lack a unified acoustic center (convergence of each speakers' axis) - is car audio's largest obstacle. overcoming them requires a full custom build with lots of fabrication. not impossible, but certainly not practical for the majority of people.