I have a SD2 powering a XXX V2 in the Wet Sounds designed dual vented enclosure in my boat. The SD2 replaced a JL HD1200/1.
I haven't had a ton of time in the boat to tune it since installing it but so far, I'm impressed. The sub seems to sound a little smoother and have a little more control.
I do wish the SD2 had a subsonic filter, though I haven't really noticed the lack of it since changing from the 1200/1. The SD1 will have it once it comes out so I may upgrade to it just because.
Here's my enclosure: