Well, I didn't even answer the first one, because I don't really know how to answer any of them. The only question I was confidently able to answer was the crossover frequency question (which I answered "don't know.")

I have a sub, because it came with the sound package on my vehicle. I won't be purchasing a new sub for the vehicle, and I have no idea what my next vehicle will be, so the survey answer I'd select for my current vehicle (compactness) may not be relevant for the next one. That theme sort of follows through other questions, too. My current sub enclosure is plastic, but it's hidden behind the back seat. If I had a sub in a trunk, I'd probably prefer matching carpet.

I suppose I could describe my ride (a truck), but a truck is very different from a van, and drastically changes the options for putting in a sub. As far as cramming a sub and amps somewhere, my ride is probably closer to a sporty 2-seater with no trunk, than a category that includes a van. If the point of the question is to find out what sort of market there are for various types of sub designs, the vehicle classes are poorly divided.