If you want clean sound you can look into any kind of sub really in 10s and a sealed box. Sealed will give alot of clarity back to you. I prefered my 2 10" Type R's becuase I listened to all kinds of music and not just booming loud music. My next setup is going to be a single 12" Eclipse Aluminum sub. It should be enough for me and I agree on the whole trunk factor. Sometimes I want my trunk and other times I say if I wanted trunk space I would have bought an SUV. Anyway thats what I recommend as far as subs go. And remember buy a decent headunit that can control and tweak your components well. I have always used pioneer and my latest model I have of theirs is excellent with hpf and all sorts of goodies.

98' Eclipse GS- Hahn Stage 2- SOLD
02' Honda S2000- SOLD
04' Acura TL- Current Whip