I suggest waiting to buy a subwoofer, until you have bought the house. If you are currently looking at houses, then you have no idea what you will end up with in terms of the size of the room. The size of the room is very important. You could overdo things and just get a massive ported model, with tons of output, right now, but then very soon you would have to move that big heavy thing. What if you end up with a small sealed room and then there isn't enough space to place it optimally?

If you are looking at a newer home, most likely if you are placing the equipment in the living room, it would be a massive open concept room, which calls for huge output subwoofers, if you want tactile feet when watching movies. If you have a dedicated sealed room that is smaller, then you might be able to get by with smaller sealed or ported 12" subs.