I recently got a 12" Alpine Type R (from JonMR2V1, thank you very much BTW ) and a more powerful amp to run the sub. Man it really makes a diffrence, and I can no longer effectivly use my RVM due to headlights being oval and 5 ft in diamater.
Today I went to BBY and picked up a pair of 6X9 Alpine Type R's and a pair of Pioneer 6" front speakers, and hooked up my 4 chanel amp to run them at reccomended RMS.
I have to say WOW, it really makes a diffrence, the sound is so much clearer than I have ever heard and the bass(when I want it to) is so hard you can feel it in your chest.
I really needed the 6" speakers for the front because my old ones were getting a little distorted, but I was planning on taking the Type R 6X9's back and picking up something a little cheaper, but now that I have heard them I may have to take the 6" back and get Type R 6" fronts.
I used to be an Infinity fan after many Subs and a complete system in my Jeep, but these alpines are just amazing. So much better than the Jeep was with a full Infinity system, and that had stock sound dampining stuff. My Acura has absolutly none of that(for now) and it still sounds better.
A buddy of mine has a 12" Type E sub, and it sounds great, not quite as much oomph as the Type R. Great sound quality, less BOOM.
If you are thinking about up-grading your system take a look at Alpine's line, you cant go wrong. I am very happy with my Alpine exprence.