Subwoofer for music only ?

That's a small room.

How do you posture yourself to listen to music?  Do you sit on a chair between the speakers?  Do you sit at a desk?  Do you lie on the bed?

For the best listening experience in a small room like that I would first get rid of the bed.  If that is not possible, then you could probably sit on the edge of the bed, pull your speakers several feet from the wall, and move your sub around until it sounds good.  If you have two subs it will be easier.

I use a single REL T/5x in 16' x 22' room and it sounds great with a pair of Harbeth P3 ESR speakers.  Plenty of bass for me.  If you are a huge bass hound and play a lot of EDM and hip-hop at high volume, I'd shoot for a T/7x in that tiny room.  There are other subs, but for my room, speakers, and listening habits the REL t/5x is perfect.  YMMV.

Will your wife be in the bed with you? She could adversely affect the listening experience, or possible enhance it depending on the resonance of the room. 

You are in a small cluttered box. You cannot produce sound waves that can expand much and therefore all that owned is unfulfilled and distorted.  You actually degrade your sound as you get lower in a room like yours, so if you’re going with a sub because you buy into this,set your blend at 120hz. The point is to ease the requirements of your woofers.  You’re much better with a good set of stereo speakers that get good extension. The main point of a subwoofer is low end support not extension. Do you really need your room to shake when the tyranausorous rex walks across your tiny screen in your bedroom? It’s pure distortion. Lastly, watching tv or reading in bed is flat out disruptive to sleep. That’s a well-documented fact based on numerous studies. 

ATC C1 MK2 subwoofer

Highly recommended

The SVS SB1000 Pro would be the ticket, assuming it's sealed/acoustic suspension, like my SB1000. That's the type of sub you need in a 13' x 13' room (same dimensions as my home office).