I had considered REL, Vandersteen, Martin Logan, and Thiel's very own SW1, but ultimately I ended up with a Velodyne DD-12. My dealer recommended them straight off the bat, but being skeptical (and having heard some lower end Velodynes), I kept looking. After auditioning one with my Thiel CS3.6's (which do not need a sub in any room without serious bass issues, which my listening room, unfortunately, has in spades), I was sold. This has been the most significant improvement that I have made to my system, and trust me, I made many more fiscally significant upgrades, but none made the level of sonic improvement that the DD-12 has. The Digital Drive series line of subs are highly configurable, and can really interface well with almost any room or system. For the 1.6's, a DD-10 might do you, depending on the room size.
Subwoofer suggestions for thiel 1.6?
I'm considering what would be a good sub match for the Thiel 1.6, aside from thiel's very own powered sub (which is something like $5,000 new.) Anything more affordable to recommend? I'm really interested in rounding out the bass on a select few rock recordings. For 90% plus of what I listen to, including rock, I'm happy with the low end of the 1.6.