This will be interesting... I've been doing the same thing (mapping it all out). I currently have a system which is all active except for the tweeter HP on the R doors, which I rarely use.
But since the MS-8 seems to be capable of correcting phase and time anomalies as a subset of a channel, rather than simply the entire channel (Imprint should be too, but I don't know if it is...) that means I *could* go back to passives on the front doors.
Since the E9x have the same path lengths from the RF mid and tweet and the LF mid and tweet, the only added phase delays other than those occurring within the driver motor and piston itself) are created by the passive filters, but those aren't negligible. Since the MS-8 corrects those, going with passives should be fine.
I am also gonna have to order the center channel trim. I have an Integra 4 to use up there. Is there a tweeter next to the mid up there?
So I've been thinking of running (DELETED four) three Arc Minis:
Mini 4 on the front and rear doors
Mini 4 bridged stereo on the underseats
Mini Sub on the trunk sub
An MS8 plus those should work pretty well... and the Class G/H amps (can never keep those straight, know it's only one, can't remember which) will still sound better than Class D and draw a hella less current than my three Zapcos at present. I like the idea of that much dynamic headroom.
I've had bad experiences with deck power ICs and passive xovers with inductors in them (second order filters and up). I know the TSX "amp" (which is two deck power ICs) did NOT like passive crossovers more complex than a series capacitor. I think that the parallel inductor "looks" like a short to some of those ICs.