IMO it's overkill, unless you want to make your trunk rattle and stuff.
I would go for something like this if you just want to add some thump, but that's just me.
Yeah I'm only looking to add a single JBL 12, so I was curious if I'd even need to dynomat the trunk, but I definitely don't want the obnoxious metal rattling sound outside the car.
I like Arden Audio for anything that isn't a custom job. Their prices are the best in town and they are usually cheaper than Amazon.
With a CRV make sure you have them disable the Active Noise Cancelling or you'll get crazy feedback and a hum through the Subwoofer.
Since it's a hatch you don't need to go too crazy to get it sounding loud in the cabin. I'd look into a powered subwoofer like these. https://www.amazon.com/dp/B0854N47QN/ref=cm_sw_r_apan_i_4WAJ8VKZTX4M51P0PXRM
I had a similar JBL powered 12 in a Crosstour and it slapped.