I was all set to buy a Thiel sub, but I had some very unusual room acoustics to deal with. My dealer (and Shari at Thiel!) recommended the Velodyne Digital Drive series, and I now have a DD-12 in my system working with my CS3.6's (which, IMHO, would need no help at all on the low end in a "normal" room). The DD-12 blends in remarkably well, and has thoroughly impressed me. The EQ and tweakability options are not only extensive, but are very, very useful. If you have been reading the mags (TAS, Stereophile, etc.), the DD series has been getting very good reviews. I certainly am thrilled with my DD-12.