Wilson Watch Dog suitable amp

I've just acquired a Watchdog II and I'm looking for advice on best amp choice.

Rest of system is YG Anat Studio driven by Halcro dm88 amps, Ayre KX-R pre.

What have other Wilson sub users chosen to drive the sub?
Bought a Velodyne amp for this sub. Works very well and the addition really adds weight to the sound.
Dave is using a Parasoud A21 to drive his Thor's.