IMHO, Velodyne's DD software/interface is great, the actual subs maybe less so. The Velo SMS-1 controller provides the benefits of the digital drive interface (at <$500 street price) for use with any sub of your choice. I've been using it with mediocre Velo SPLR8 subs, but just ordered a pair of 12" Rythmik Audios to replace the SPLRs. The JL subs get a lot of praise and test out extremely well, but the much less expensive Rythmik and SVS subs produce pretty impressive results, too, and offer an awful lot of performance for the $.
Good Luck
Marty
PS: Since the SMS - 1 works in the digital domain, its high pass will subject the main signal to A/D/A conversion. If you don't want A/D/A conversion in the main signal path, a ($300) NHT X-2 (or similar) can be used to roll off your main speakers without the A/D/A and without spending a billion $.
PPS
Good Luck
Marty
PS: Since the SMS - 1 works in the digital domain, its high pass will subject the main signal to A/D/A conversion. If you don't want A/D/A conversion in the main signal path, a ($300) NHT X-2 (or similar) can be used to roll off your main speakers without the A/D/A and without spending a billion $.
PPS