Here's a photo of my Sub box. I've got two 8" KLIPSCH Subs installed and two way rear speakers on each end with base ports. I installed an Alpine IVA-D310 Audio / Video system and it sounds real good IMO. I kept the existing Amp with stock speaker and sub system and added an Alpine four channel amp to handle the additional rear subs and left / right rear speakers for the full surround effect. This is plenty for the size of this car (makes my hair dance).
There are more photos in my User Gallery. As you can see, the box doesn't take much space from the original cargo area.
Peace... Fritz