My listening room is a small space too (about 13x14). I have Thiels.
I have repositioned my speakers and furniture many times. To get the big 3D image, you will need to give speakers about four feet of *clear* space behind, and clear as much from between as possible. You'll get a wider, deeper, taller soundstage; also tighter and more realistic bass; *everything* improves in a big way that throwing money at more components and tweaks cannot get. Your speakers will get more living space than you, but I have not found another solution.
On the subwoofer, I do not think that it will be very meaningful if you don't pull those speakers out first. It's like improving a sportscar that you never take out on the highway.
I have repositioned my speakers and furniture many times. To get the big 3D image, you will need to give speakers about four feet of *clear* space behind, and clear as much from between as possible. You'll get a wider, deeper, taller soundstage; also tighter and more realistic bass; *everything* improves in a big way that throwing money at more components and tweaks cannot get. Your speakers will get more living space than you, but I have not found another solution.
On the subwoofer, I do not think that it will be very meaningful if you don't pull those speakers out first. It's like improving a sportscar that you never take out on the highway.