Linn Sizmik 12.45 subwoofer - How good is it?

I have custom Focal drivers in a TMM configuration (7W411 7" W-cone, same as those used in the Utopias).  I am considering a Linn Sizmik 12.45 subwoofer.  I have a Jungson JA88D integrated amplifier.

How good is this subwoofer and would it be easy to integrate with my Focal speakers?

Is there another used subwoofer that you would recommend if the Linn is a poor choice?