XLC's are old fosgates.
In reality they arent bad subs but they are equivilent to ... todays HE's i'd say.
The 18 is a large driver is going to move air but fosgates already suffer from bad sq and I can just imagine how an 18 would flex. I had a set of xlc 12's back in the day and for what I payed for them they were a pretty good sub.
If your buying it new, I'd look elsewhere firstr
I used to spend a lot of my free time here. It was fun I suppose. Still rocking the 9515 and Better Audio amp haha.
How's incriminator stuff these days?