I think it's a DC sound labs, or something like that.
Also, you have that space, but you don't necessarily have to use all of.
If you're really looking a sub where output isn't your first priority, which it shouldn't be in a SQ type install. My choices would be a Dayton HO or HF since space isn't a problem, a DIYMA R12, or a Peerless XXLS. I've used the first two, with excellent results, never used the Peerless but it always gets great reviews and if their subs are anything like their mids (which I've used) then they are well worth it.