I have owned the previous version of the Sunfire True Signature, and it was a woderful sub. Also, I have heard the DefTech before, I don't think it is in the same league, my opinion, as the Sunfire as far as depth, speed, or flexbility. It does look a lot better though.
If you are looking for a 2 channel system sub though, I would have 2 suggestion: 1) Vandersteen 2wq, it is built for music not video or hybrid, read the forums, it is not expensive and a great piece of equipment, 2) Velodyne DD- 10, 12, 15 depending on size. These are great subs, they go very, very deep and the programming flexibility is unbelieveable.
If you are looking for a 2 channel system sub though, I would have 2 suggestion: 1) Vandersteen 2wq, it is built for music not video or hybrid, read the forums, it is not expensive and a great piece of equipment, 2) Velodyne DD- 10, 12, 15 depending on size. These are great subs, they go very, very deep and the programming flexibility is unbelieveable.