Last week I had to set up a system using an alpine 9887. It was two way front speakers and rear sub (as usual).
The wost of all about 9887 is the control interface, it's really depressing and frustrating. The interface in previous series was messy too, but not that terrible. Menu layouts and key sequences to access functions such as delays, crossover and parametric EQ will make you wish to smash the 9887 with a big hammer.
On the other hand, it features the 6 usual delays (althouth the linked adjustment mode of the previous versions, called "bass focus", is missing!!! damn fools!!! this mode was very useful to find front to sub delay...) It also features 3 crossovers with adjustable frequencies and 6/12/18/24dB/oct slopes but it still doesn't allow to set the type of crossover (Butterworth, Bessel, Linkwitz-Riley, etc...) and the type employed is just undefined! The parametric EQ of the previous versions is also there, with the usual stupid limitations (you can't set two bands too close and there are only 3 Q choices).
A $250 behringer DCX2496 can be modified for car use and has like 5 times more functionality than the most complete DSP headunit. It has 3 inputs and 6 outputs. Outputs have independent adjustable phase-shifters and low-pass and high-pass filters (6/12/18/24/48 dB/oct, Butterworth, Bessel, Linkwitz-Riley). Up to 9 parametric EQs can be set on each input and output (CPU power allows up to 36 simultaneous with 3-way stereo LR24 filtering). Inputs and outputs have independent delays, routing and limiters!! (no more blown speakers) Control interface is nice to the point that this DSP is used by embedded non-adjustable DSP designers of other companies to find out optimum system parameters in a comfortable way. It has everything you would dream to have (but will never find) in a car DSP.
Some other pro-audio digital crossovers are even better (and some expensive ones are actually worse!!) but they cost $500 to $5000 rather than $250 (see Xilica, BSS, dbx, BBE, etc...)