HAHA, I thought I was the only one who knew who Haystack was. I have one L710 and a 600.1 Xtant in my s-10, and it is plenty loud. Sure 2 would be louder, but really, what's the use, I don't do SPL competiton or anything.
BTW, I have a W3 in my Stang, and I am happy with it.