Well, I have decided to add a sub to my 300c to reinforce the deep end. Stock head unit will stay.

I have always like XBL^2 drivers in home theatre subs, so I think this will be a good starting point. I am thinking 2.5ft^3 sealed box with a 1000W amp. Seem like a reasonable plan?

 

Seems reasonable to me. Never got a chance to throw mine in my car, but I've been quite impressed with my SDX15 for home theater.

 

Nice!!!!!!!!!!!!!!!!!!!!

 

I am going to build my own box. This is the first car sub build, not speaker build though. Do you fasten the box the trunk?

 

you should