A little off topic as far as the audio goes; those vans have well known transmission problems. the first thing you need to do with the van is get the transmission serviced. Try to find a shop with a transmission flush machine and have it flushed. And make sure that a good brand of trans fluid is used when it's changed. No matter what the manual calls for, have it serviced every 15 to 20k.
The van got regular and thorough maintenance.
Trans got fluid changed about a month before we bought it -- probably dealership.
It is as mechanically sound as a used 127k vehicle can be.
The last suggested maintenance item was PS flush -- I'll do that myself probably at 1st oil change.
Prob needs some front end stuff - there are some creaks and noises that I would like to improve.
From what I've read sway bar bushings on these wear easy and are noisier than most cars.
In my experience - it is a safe bet that an automatic transmission WILL fail at some point. USUALLY
We who choose to drive po' folks cars are willing to take that risk and eat the ~$2k rebuild if it comes to that.
But back to the audio -- I'm seriously considering a fiberglass sub enclosure. I did one in a trunk years ago. Wasn't much fun, but I did like the results. I think this one would be quite a bit smaller and less time consuming.
Not sure about how/where I want to mount my amps. If the sub enclosure goes well I may consider something with fiberglass for those as well.