I'd like to get your input on the best sub for my Rx330. Here are the details:

I'm going for SQ and have absolutely no interest in losing my hearing or winning SPL contests.

Front: Biamping either: Dynaudio 240 MkII, or Dyn 360, or Boston Acoustics Z6
Rear speakers: Boston ProSeries 5.5
amp1: McIntosh MC440 (50Wx4@4 ohms + 100Wx2@4 ohms)
amp2: McIntosh ?? probably MC427 (100Wx2@4 ohms) ??
Head: Factory (non-ML)
Processor: Alpine PXA-H700

sub: single 12", mounting depth <6", sealed enclosure, preferably small. It'll be firing out the side in a custom enclusure that should lie flush with the wheel well in the rear cargo area. Most likely powered by bridging 2 of the 100W McIntosh channels. I'm slightly overbudget on this system and I don't think I'll be able to afford a McIntosh monoblock amp.

I've been leaning towards a Boston Pro 12.5LF, because I'm comfortable with Boston, but I'd be interested in hearing what other brands are out there that are worth considering.

I know Percy loves the Velodyne (and I adore my Velodyne F-1500 home theater sub), but I've talked with the Velodyne people and they regard that sub as a nightmare that was very difficult to install correctly, and they have absolutely no intention of returning to the world of car audio. So, I'd like to get something that has a little bit better customer support.