I would love to have multiple subs but I think my neighbors would want me out of my apartment, lol! What I'm really looking for is a good, musical sub that can dig deep and hard! I'm just looking for the best sound reproduction that I can afford and get away with here. Good sound quality at low to medium volume is very important to me because I don't want to damage my hearing anymore than I have already.
Personally, you're going want more than a single RW-12d if wanting to replicate expected DNB like in a club. More like four RW-12d's would be more like it or a pair or three of upper output ID subwoofers but now you're pushing $3k or more. It's all going be dependent on how far you want to push the issue or what your expectations are going be.
The Klipsch makes a great starter sub. You can add another to it when the opportunity arises. It's my second, and I was able to get it to blend very nicely with the one I had before.
Still not club DnB, perhaps, but great for family room movies.