Mojo or MT.
I heard 3 18MT off of 5k+rms and was VERY impressed. But since you're looking for something a little more mild..
In the store we have a 15'' MOJO in a prefab off of a Memphis 2500 and it is STUPID loud. A pair of 15'' M1 ported off of the 2500 still wasn't as loud as a single mojo. The single Mojo was also louder than the rest of our wall put together.
It will wang off of 1000rms but when you throw unlimited on it, it is ridiculous. Even more impressive to me than the sub is the amp. But, that is a whole nother topic.