In my opinion, the dipoles on your list are quite likely to work well. I have customers who have used very large dipoles in rooms smaller than yours and been very happy. You'd need to diffuse the backwave in the interest of good image depth.
Dipole bass doesn't have the impact of bass from a box, but often has better pitch definition and many people think it sounds more natural.
Another type of speaker that works well in a small room is a monopole with a well-controlled radiation pattern to minimize early sidewall reflections. In this category would come horn-based speakers small enough to integrate well at fairly close range, single-driver speakers, and coaxials. You want to minimize early sidewall reflections because those are the ones most detrimental to imaging. Using diffusion at the first sidewall reflection zones helps. Try to avoid using absorption any more than you have to, as particularly in small rooms too much absorption sucks the life out of the sound by killing the reverberant field.
You specifically mentioned "subtle natural sounding bass that's deep and accurate and projects depth." That delicious sense of enormous acoustic space that well-reproduced stereo bass can provide is largely generated by a phase difference between the bass signals arriving at the left and right ears. The phase differential in a recording with true stereo bass is best reproduced by stereo subwoofers located to the extreme left and right of the listening position.
I have avoided making specific suggestions here because many (though not all) of the speakers I'd suggest are ones I peddle. Finding speakers that work with, rather than against, small room acoustics is something I've put a high priority on. Shoot me an e-mail if you'd like some specific suggstions (and don't worry they won't all be stuff I sell).
Duke
Dipole bass doesn't have the impact of bass from a box, but often has better pitch definition and many people think it sounds more natural.
Another type of speaker that works well in a small room is a monopole with a well-controlled radiation pattern to minimize early sidewall reflections. In this category would come horn-based speakers small enough to integrate well at fairly close range, single-driver speakers, and coaxials. You want to minimize early sidewall reflections because those are the ones most detrimental to imaging. Using diffusion at the first sidewall reflection zones helps. Try to avoid using absorption any more than you have to, as particularly in small rooms too much absorption sucks the life out of the sound by killing the reverberant field.
You specifically mentioned "subtle natural sounding bass that's deep and accurate and projects depth." That delicious sense of enormous acoustic space that well-reproduced stereo bass can provide is largely generated by a phase difference between the bass signals arriving at the left and right ears. The phase differential in a recording with true stereo bass is best reproduced by stereo subwoofers located to the extreme left and right of the listening position.
I have avoided making specific suggestions here because many (though not all) of the speakers I'd suggest are ones I peddle. Finding speakers that work with, rather than against, small room acoustics is something I've put a high priority on. Shoot me an e-mail if you'd like some specific suggstions (and don't worry they won't all be stuff I sell).
Duke