if a 3-way/4-way setup is definitely an area you want to go, i highly recommend a DSP. especially for you, @
FR-S2GT86 with your 4-way setup.
i installed the dayton dsp-408 in my truck specifically for more advanced crossover control (needed a 400hz x-over on the high freq drivers, deck stopped at 200hz, or started at 1.2khz in network mode), and the featureset is highly adjustable. each of the 8 outputs can have it's own independent parametric eq, as well as time alignment and phasing options. it does exactly what i built a $1500+ carpc for a dozen years ago for under $200!
the minidsp 6x8 does a lot of the same thing at a slightly higher cost as well..