I just bought a PC12-NSD this past week, and so far I'm really loving it. It looks great, has bass you can truly feel, and shipped very quickly.
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I'm pretty new to having a full speaker setup, and this is my first real sub, so I probably won't be of any use for your comparison shopping.
However, I just watched "Wanted" last night, and was very impressed with how low the bass was and how much you could feel the LFE. I have a relatively small room with openings on 2 ends of one wall, and it still comes off as very powerful. I'll have an SPL meter next week to really test it out, though.
I looked obsessively online for subs over the past few weeks, and comparing response curves and user feedback, and SVS always seemed to be in the top 2 manufacturers. In the end I chose the PC12 because of its small footprint and how low the freq response extended. Plus the price is unbeatable! Including shipping it was less than $600. I had looked at HSU and AV123 as well, but their shipping costs took them out of the running.