I was in a similar boat with my Mazda3 hatchback - With packaging as your top priority, that will likely affect your choices more than variations in the sound signature of different sub brands/models.
One really convenient placement option in a hatchback is the side of the rear cargo area, but you'd need a custom enclosure for the woofer. I lucked out with the Mazda--there was a guy making custom boxes that took the place of the jack cubby. This isn't mine but it's the same idea: https://www.mazdas247.com/forum/prox...c4cac1fa4898ac
A competent custom shop could build something like that, but it might exceed your budget.
So, the key piece here might be finding a reasonably-priced off-the-shelf enclosure designed to fit in a tight spot, and then reverse engineer a suitable sub from there. Most of the compact enclosures are designed for 8" or even 6.5" subs. Here are a couple:
Most of the shallower small subs that would fit in enclosures like these can typically only handle up to 200w or so RMS. The high-power-handling small subs tend to have big magnets that increase the mounting depth quite a bit - and once added to the amp and enclosure, might be beyond your budget. The one in my Mazda is a 200w sub, and it definitely falls into the "fills out the bottom end" category, as opposed to the "blow the windows out" category.
You'll also need to think about where the amp is going to go - I've got mine under the driver seat, which you say is one possible spot for your sub - my Mazda wouldn't have enough room for both the amp and sub under there. Maybe your C-Max has more room, or maybe you could put the sub under one seat, and the amp under the other.