How to make my bass better?

Hello, The car is a 1985 Mercedes 380SE. I recently installed a Nakamichi CD-400 head unit and ran via 13 guage (or maybe 11, I forget) IXOS wire (it was directional and gamma threaded) 2 alpine sps-460a's in the rear and 2 alpine sps-080a's in the front. The sound is good, but when I crank it loud the bass starts to distort. I don't blast bass or listen to rap, but it happens with like john lee hooker or any somewhat bassy music (Chuck Berry, Foreignor, stuff like that). I don't want to put on bass blockers because most of the time I am not listening to the music loud, and I don't want to needlessly get rid of certain frequencies. I'm told my only choice is to add a sub (the people at crutchfield recommended the Kenwood KSC-SW1). So my questions are these: What do you all recommend I do considering my listening habits (classic rock, oldies, classical, talk) and that I want to make as minor modifications to my car as possible. If at all possible I want to avoid doing anything irreversible, including screw holes. How would I go about installing this? The Nakamichi head unit has a seperate subwoofer control so I'm guessing the wiring is simple. I also want it to be something that you would never know is there from looking inside the car. It's ok if you can see it when you open the trunk, but I don't want to be seen when you open the car. That's another thing, I want it to be as light and small as possible.

Also there are three deal breakers: it take up substantial space, it requires an external amp (i.e I can't wire it into my Nak head unit), or it requires you to make a cutout.

Thanks,
Rihcard

Check out Car domain here https://www.cardomain.com/shoptype/Enclosed+Subwoofers

They carry powered subs from Infinity, Bazooka, Kenwood and Clarion.

I would suggest either the Infinity Basslink or a Bazooka Tube.

Chris

I've never gotten a chance to listen to an Infinity basslink but I have heard really good things about it. Crutchfield did a comparison of the Kenwood w00x (which is similar to the kenwood power sub mentioned above) and the Infinity basslink. Here is a link to it.

https://www.crutchfieldadvisor.com/S-NaCdveKwIjU/reviews/20040413/bass_reviews.html

Customsuburb,

I have heard a few Basslinks and was actually quite impressed. I am actually thinking about installing one in thw wifes Astro as she wants just a little better bass responce as it already has the high end Bose (Yes Bose) system in it.

Chris