I've had so many since the mid 90's it's hard to pick. I had a set of pheonix gold xmax 15's running off a PG zx600 each and I think it may have been my favorite substage ever. Surely not the loudest but had an amazing mix of quality and loudness.
AA avalanche. I would probably say the 05 RE XXX but I built it and sold it instead. //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif
2 12" w0's in a sealed box hooked up to a fosgate 800.2 when I was a senior in hs. They were in the back of a 97 Cavi w/ the fold down seat. Not sure what it was but that was by far the best sounding system I've ever had, atleast from what I can remember.
My most satisfying as far as everyday music had to be the JBL Power Series P1022 subs. I had 4 of these in a custom fiberglass ported enclosure in my old Honda Element SC. They got LOUd and sounded excellent no matter what song I was playing