I used to have an 85 Camaro with 4 Alpine Type R subs in a sealed enclosure, each sub had 1.25 ft^3 of space pushed by two Rockford Fosgate 500a amps and I hit 143.6db.
I had two of the subs in the well and two on top...the enclosure was one I built and the amp rack was between the top two subs and the bottom two and it was all built as a one piece unit. I unfortunately do not have any pics.