Putting a sub in or on your armoir may cause buzzing and rattling that will drive you crazy. Being a bedroom system I would not go overboard with multiple subs. I would go for small and good looking if it is in a visible location. Match your furniture if possible. There are lots of people that rave about the Martin Logan subs as good performers in a small package.
Multiple subs can help smooth out bass humps/holes in your room frequencey responce. This is a square bedroom with a giant bed in the middle. This is far from ideal theater design to begin with. Multiple subs can also cancel each other out resulting in less bass or muddy bass. Hook-up and set-up can vary depending on home theater or stereo applications. If you plan on watching movies in bed then I would just use one sub on the LFE output. Keep it simple.
Multiple subs can help smooth out bass humps/holes in your room frequencey responce. This is a square bedroom with a giant bed in the middle. This is far from ideal theater design to begin with. Multiple subs can also cancel each other out resulting in less bass or muddy bass. Hook-up and set-up can vary depending on home theater or stereo applications. If you plan on watching movies in bed then I would just use one sub on the LFE output. Keep it simple.