For the interior, my very first mod for this car was a Eclipse Titanium 12" Monster Subwoofer, and a Rockford Fosgate amp rated at 500 Watts @4Ohms. I run the AMP at 2Ohms, with an impedence equalization circuit, generously designed, and fabricated by a brilliant co-worker of mine Benjamin Nielsen.
Sub:

Amp:

For a box, well I tried at least 10 designs. I settled on a HUGE box that was so big I had to build it in my trunk. It features a slot port, and over 6 Cubic feet. Designed by a guy on Sounddomain good240sx or something like that, I'll get his name right soon. He knows his shit, and is highly recommended to design a custom box. I built a custom amp rack along with it, nothing fancy, but it hides the wires.
Here it is:

I ran the subwoofer switch into the coin holder, and hid the base boost knob near the seat. The car looks like it has a shitty stock stereo when you look inside:). I ran Infinity Kappa front components, and removed the rear fill.
I also added some lights, which I cleverly converted the map-light switch into one that would turn on the Neons for the SUB.
Pics didn't turn out...
I wanted to monitor Boost levels from the supercharger, and get a warning of dangerous lean conditions with an Air/Fuel gauge that are prone with a boosted vehicle. I wired the Air/Fuel gauge into pin 87(Red/Black, Left front oxygen sensor) and pin 60(Grey/Light Blue, Right front oxygen sensor) from the computer. I ran the oxygen sensor wires to a 3 position switch in the ashtray, along with switches for the Intercooler fan, and gauge lighting.
Heres a shot of the Autometer Air/Fuel and Boost Gauge and my son posin(see that 40K original Miles!):

I wired a switch panel into the ash tray, so it would be covered when needed(had to keep the Cig lighter) The silver one is for the left/right bank oxygen sensors:

Every electrical connection in my car is SOLDERED for durability. I also installed a Audiovox alarm, with some neat starter disable circuits, so don't even think about it!
For the exterior I cut the springs, and flattened the top coil. I added a spoiler, which I planned on painting, but then I decided to make it unique, add some black vinyl stripes, tint and Vent Visors for a unique appearance, that isn't too flashy. I really like the looks, and I'm keeping those V6 wheels so everyone knows what I'm packin!