I'd personally go with a pair of svs sb12 nsd's. I had an svs sb12 plus which was the predesessor to the sb12 nsd and it was a great sub. I would have kept it but the color didn't match the rest of my gear, and I was having a hard time finding another one (I wanted two because two gives a more uniform sound with more headroom). So anyways, I sold it and when I'm in the market for subs again, I'll probably get a pair of the svs sb12 plus'. I remember seeing awhile back that they had a slight discount if you bought a pair; might be worthwhile to ask them. All in all, my svs played pretty low (22 hz?) and was pretty fast and the new sb12 nsd is supposed to be even faster with less overhang. I don't think you'd be disappointed in any way with a pair.
