Reasons and Options
Well, i have a mandate from the girl-fiend that there can be no speaker "thingys" in the room. And I am on a pretty limited budget and most in wall subs are out of my budget. We are not looking for a lot of bass. So I would probably only get an 8" sub.
What are the reasons that you can think of that this would be bad?
Keep in mind that we are not audiophiles and just about anything would be an improvement on what we've had before.
I have about $100-$150 to spend on a sub.
Some reasons which come to mind are:
- The dirt/dust factor JGarcia mentioned
- Opportunity to have someone step in/on it and destroy it

- Once you select a location, you are stuck with it (or a hole in the floor)

- Inability to move it, if the acoustics you seek don't work out or GF decides to "re-arrange the furniture"!
Other Options:
- A small, inexpensive under couch (or tucked in a corner) subwoofer such as:
This one or for a bit over your stated budget
this other one
These are not "the world's best" subs, but they would probably meet the requirements you put forth--decent bass, out of sight, and inexpensive.
Cheers,
XEagleDriver