I used to own the ML Grotto (not the "i" version). It was an excellent sub for music. In fact I would say that it was one of my favorite subs that I've owned to date, for music. The servo design really kept it super clean & ill tell you, that driver could MOVE!!
The issue I had with it was that being a sealed 10" sub it just didn't have the output that I was looking for when it came to movies. I would many times push it into protection mode & it'd shut off (as its supposed to) About 2 years ago I sold it to my neighbor across the street from me for $400. He was looking for a sub that is used in a Music only setup so it was a perfect match. I still get to hear it once in a while when I'm over there & I still love hearing it. Had it been a 12" or 15" version I'd probably still own it.
So depending on your room size, listening habits, whether you are into music or movies & what the price is, I'd say at least consider it. If your looking for a high output sub for movies...no! But if you want clean, accurate bass for say a 2channel music rig then yeah it's perfect for that!
Hope this help!!