This might be too much information, but here's what I've learned so far. FWIW, this is an intersection of multiple areas of interest that I play with to keep myself entertained.
I wanted a double din unit (the old cutout is less than true double din, but thankfully so are most of the units) for a backup camera which is handy when making a 256 point turn around on a trail with a steep drop off in an EB. In terms of sound quality the higher end kenwood units that include a dsp (with crossovers, a little bit of EQ and more importantly: time alignment), but once you put those together, nav gets dragged in, and the thing is somewhat expensive. This is not wonderful for something I don't drive every day, and may get a window smashed, and I do leave the van parked at trailheads for multiple days at a time.
So, I ended up with a mid-range pioneer (AVHX4600BT), also partially under the assumption that I'll replace it with something that has more modern/better bluetooth at some point. A friend that I ride-share my sfbay <> tahoe commute with got whatever the high end kenwood unit with a volume knob was last year and it's way nicer than my pioneer. (Just going there is probably the smart choice, unless you're pinching pennies.) Off-line nav of some sort is actually nice to have as well in a 4x4 camper van, I've had to resort to hiking maps and a gps a couple of times.
I got annoyed at the lack of a twisting volume knob, so I built one that could talk to the steering wheel button remote input. (Cute little microcontroller project, honestly I did that mostly for the experience of seeing what the tool-chain in that space looks like today, which is useful for me professionally. -- This is not entirely trivial, the input needs to be rate limited.)
I cracked recently and ordered a minidsp unit to fix time alignment with the sub that's under the bed. FWIW, I'm playing with it right now in my living room. It's an amazing tool, and even adding that up with my pioneer, I'm way ahead of a nav unit in cost, but I obviously don't have nav.
Also relevant to the camper van situation: I'm sticking with class-d amps. Rocking out on battery for the better part of an evening is less of a draw than putting the arb fridge into freezer mode.
Finally, this is sometimes considered a matter of opinion, but getting a dedicated amplifier and driving just two channels with it is going to have much better results than driving four speakers off the head unit. -- I say sometimes, because the folks who disagree with this know that they are wrong and are just doing it to wind me up.
Brianjwilson: That unit was fit in the dash cutout really nicely! -- I had some issues with the older dash and never found a shroud that really fit well, and just ended up centering the unit carefully and leaving it like that, but whatever was done in your case looks way better.
My pioneer back up video is not instant on, but is way faster than my friends kenwood, which has actually frustrated me a couple of times, so that is perhaps a feature to look for.