I'd wager a PA 21" cone would turn into confetti with what someone would do with it in a car.
I'd doubt it. Some pro audio cones are built for horn loading, which puts WAY more pressure on the cone than you'll deal with in car audio, outside of 180db extreme class cars. Compared to the upgraded DD cone, no it won't hold up like that would, but compared to 99% of car audio drivers, they do fine, even in an abusive daily application.. D
Anyway my current subwoofer is the speaker that recone is for and it works fine in the car. It's a very stiff paper cone, very thick tinsels and durable thick spiders. The woofer doesn't need a huge box all things considered (bl/re of 310, strong neo motor with a 6inch coil), handles 3k like it's nothing AND will play as high or as low as needed. I could use the thing as a retard midbass if I wanted to and it flexes my steering wheel at 20hz. I see a least one post a day on here from people who complain they can't hit 70hz since they're tuned at 30, no it's cuz your woofer is ****. I'm tuned at 30 right now and can play up to as high as my ms-8 will go with no problems.
Part wise for that kit, stiff suspension, never seen it bottom out, I tried to free air it on a 1200 watt amp and even with 20hz tones it wasn't near bottoming, the suspension seems to keep it around 25m of excursion.. For playing music I'd take it over 99% of what's out there right now for SQL. Not a fan of the accordion surrounds, I'll be honest but that's my ONLY complaint. So I'd still go to IA for this because without a VERY strong motor you won't move that spider easily, most 3inch coils wouldnt' stand a chance.... Just saying, don't knock it until you try it
edit: Someone mentioned the 24 SHD, I DO want to try one of those as some point, assuming the T/S seem useable. Someone mentioned 20hz recommended tuning, which makes me thing the T/S may not be great for a car audio application. I've never seen a driver need lower than 25hz for a semi-flat in car response, if it was made for ported in the first place.