The unfortuate thing is that dont have enough space to put 12's in the place where 10's are. I do have a pair of "boat shakers" (13W6's on HD1200 amps) in the rear lockers so they do provide some low bass.
I would like to get more out of the direct radiating space I have. Bottom line is I need to hear these SPL subs to see if they are right for me. That would mean buying them and taking my chances.