the 3 way coax speakers you ordered are factory location replacements and do not require an enclosure.. they're also not subwoofers and will not perform in that manner..
and as already mentioned, while MDF is a great enclosure material for audio performance, it does not like water.. wet location special application speakers are available for boat and RV applications that may better suit your install..
if you want to build a high performance subwoofer/enclosure, you might want to do some reading..
http://www.kicker.com/how-to-build-a-subwoofer-box
or these guys are usually very helpful..
https://www.crutchfield.com/S-8tB1ec..._building.html
I'm a big fan of stock car audio but I do have a very powerful audio setup in my family room.. NHT 300w A1/X1 powering a W1 with dual 12" AL drivers weighing in at 71lbs enclosed that digs deep to 26hz.. with a 50lb Yamaha RXV3300 at 130w/ch powering 6 NHT L5 wall monitors, it's blown several lights in my house watching gunfight and car chase scenes.. it runs clean and crisp well above the human tolerance.. check out Super Speedway for awesome audio effects
I understand a fair amount about how drivers work but not well enough to design something as well as audio engineers.. you might consider finding something available in an existing enclosure that you can fit into your mounting location(s)..
you might also consider running the coax style 2 or 3 way in the location you're considering and installing a small subwoofer enclosure elsewhere along with a properly adjusted crossover for the performance it sounds like you're looking for..
a trip to an automotive audio specialty retail store may also answer a lot of questions along with calling the good folks at Crutchfield.. a matched set of speakers, sub(s), and amp(s) will more likely deliver the sound quality you're looking for..
good luck!