Really, only the ultimate DIY tweaker will really realize any SQ benefit from going all active.
(and since that DIY tweaker understands the issues at play - those are the things driving his tweaks at the controls, after all - the same tweaker could alternatively design a passive crossover to do the same thing
The question is: What are your standards? Your point of reference?
It's highly likely that if you purchase a good off-the-shelf component set, you'll be more than happy, and have sound exceeding that of any factory system - if you properly prep each location where the components are to be installed (and that might involve a bit of speaker aiming, as well).
Consider not just the pie-in-the-sky dreams of what you can tweak with an all-active setup, but also the limitations...
...realistically, there's only so far you can tweak your Xover point, given a mid/tweet combo. Too high, and the mid will degrade, not being able to really react that fast to produce those high notes. Too low, and the tweet will bottom out, not having the excursion capability to be able to produce those midrange notes.
And of course, there is significant additional expense here...
With a traditional passive Xover setup, you power the entire set with a 2-channel amp (or maybe even just your head unit).
With an all-active setup, you need one channel of amplification for every speaker being powered - the active Xover going before the amplifier, in the chain.
That means it's not just that you are wasting the passive Xovers that came with the set, or that you are purchasing a good quality active Xover to do the job that you want it to - but also that you need to purchase multiple amplifiers...
If budget is any concern, I'd rather see any enthusiast purchase a single, decently powerful, high quality amplifier, and use the passive crossovers that were designed for the component set (and that design - and even tweakability - is likely very good, given a good component set
), instead of spreading that budget thin, maybe buying multiple cheaper amplifiers, a so-so quality Xover, compromising on the cabling, etc.
You already know the arguments for
going all-active, those benefits.
I'm middle-of-the-road on the issue.
I have a Civic - my summer "good car" (sponsored SQ vehicle, local shop and DLS) that is currently a work in progress, but is going to be all-active, using a cool processor that'll hit the market in 2006 CES... and believe me, I'm feeling the hurt in trying to fit all these amps in here... four of them just for the SQ portion of the system, and then two bass amps for a separate SPL system.
And then I have a Pathfinder - my foul weather/winter car. it has a homemade Xover that I built, allowing a single big Alpine 2-channel amp to power 11 speakers in the vehicle (two tweets, four mids, four midbass speakers, and a subwoofer).
Both are SQ vehicles... things like imaging and detail being a priority.
It's certainly not that "passive = bad".
But there does seem to be a bandwagon - they can often inflate reality a bit.