If you went 4cu' at 33Hz, you will get a huge spike of 7.8db at 35Hz.
If you want good sq and a strong low end, I would make a box 3.5cu' and port it to 24Hz. This would give you a pretty flat response with a slight peak of 2.5db at 26Hz. You will have a strong low end (between 22 and 38Hz) The brahma can do the low notes, that should sound pretty cool.
Oh yah, a port 3"w, 6"h, and 20.5"l should get you there.
2006 Jeep Liberty
Adire Audio, Cadence, Clarion, MB Quart
Lv = [(14630000 x R^2) / (Fb^2 x Vb)] - 1.463R
*Vb = vol. in cu"
**R = sq.rt. A / Pi (for square/slot port)