I am currently running 2 12" Alpine Type R's in the trunk of my 98 vert. The sound rocks.... I am selling the custom boxes if you are intrested in them. They are custom made for the car and fit perfectly. Email me if you are interested.
You can get good sound out of them inside the car when the subs are in the trunk. However, if your sound pressure levels are fairly high, you will drive everybody insane with the sound of your trunklicense plate rattling.