First this thread is kinda pointless where as it is a vs and will more than likely be cluttered with arguments before long as they all do.. And there are to many opinions to really get anywhere
Second no matter what anyone says its your choice in which you choose, any of the mentioned subs will do you well
All that said, 18s are out there is simply no enough space, 2 12s are pushing it I personally say 3.5 cubes after displacement will be to small for those as well, one 15 would enjoy being ported at around 3-4 cubes, so that would narrow it down quite a bit..
I have heard the Q and the BL and from my personal experience I would say the Q would be more suited out of those two
Between the Q and the SSD I Cannot say because I have neve heard or seen the ssd in person, but judging by specs I still favor the Q
I don't mean to come off like a dick, just being blunt, cuz I'm tired of sugar coating everything