Best type of Sub to consider?

I'm not looking for a brand or model recommendation at this time, but rather the best type of sub to fit my room and system. If you access my System pics, you will see that I have open corners behind my speakers and that my Horning speakers are rear ported. This has caused some energy loss, especially in the bass when compared to my previous setup in my other home.

I am a newbie to subs and see different design types that fire up, down, up and down, and forward. There may be other variations. So, does any of this matter when applying the best design type to a room, my room? My knee-jerk reaction is to go with forward firing in my situation, but that's complete speculation on my part, so why I'm asking.
Kenny