IMHO, the Aeria; 9s were designed for powerful bass, not "thick" bass. As speakers go, they are very flat. Any speaker, especially ones that go as low as the 9s, need to be positioned carefully to avoid the issue your describing.
It is never advisable to position speakers the same distance from both walls as it creates strong standing waves. Moving them out from the back wall and/or closer to the side walls, even a few inches, will help. Moving them out from the back wall will increase your soundstage depth dramatically. The more you do it the better it gets; and it WILL help your bass problem not matter what your Ariels were designed for. One ideal would be 8'4" from the back wall and 2'4" from the side walls. This puts the speakers 1/3 of the way from the back wall and 1/6 of the way from the side walls. This will be a good start at minimizing standing waves. All dimensions calculated from the center of the port, or alternatively, from the voice coil of the woofers, depending on which frequencies are the most problematic.
Your listening position is a few inches from the center of the room, also not good. Again, 8'4" from the rear wall would be one ideal if you followed the above suggestions. If not, you might try moving forward even a few inches. Moving back a few inches will put you right in a hot spot.
If you implemented the above ideals, this would also put you closer to your speakers which would give you a higher ratio of direct to reflected sound, affording you the same volume at the listening position with a lower volume setting on your preamp, which would also help. Towing the speakers in will help with perceived detail.
You could also try plugging the ports with open cell foam, or for more damping, closed cell, but those drivers are not designed for sealed boxes. Mounting the speaker on good brass or steel cones will help as well, and not only the bass. The optional feet you mentioned, of course, would be one option.
These suggestions will be more effective and do less harm, IMHO. If this is not sufficient, Rives specializes in calculating specific recommendations based on your dimensions, etc. Good luck!
It is never advisable to position speakers the same distance from both walls as it creates strong standing waves. Moving them out from the back wall and/or closer to the side walls, even a few inches, will help. Moving them out from the back wall will increase your soundstage depth dramatically. The more you do it the better it gets; and it WILL help your bass problem not matter what your Ariels were designed for. One ideal would be 8'4" from the back wall and 2'4" from the side walls. This puts the speakers 1/3 of the way from the back wall and 1/6 of the way from the side walls. This will be a good start at minimizing standing waves. All dimensions calculated from the center of the port, or alternatively, from the voice coil of the woofers, depending on which frequencies are the most problematic.
Your listening position is a few inches from the center of the room, also not good. Again, 8'4" from the rear wall would be one ideal if you followed the above suggestions. If not, you might try moving forward even a few inches. Moving back a few inches will put you right in a hot spot.
If you implemented the above ideals, this would also put you closer to your speakers which would give you a higher ratio of direct to reflected sound, affording you the same volume at the listening position with a lower volume setting on your preamp, which would also help. Towing the speakers in will help with perceived detail.
You could also try plugging the ports with open cell foam, or for more damping, closed cell, but those drivers are not designed for sealed boxes. Mounting the speaker on good brass or steel cones will help as well, and not only the bass. The optional feet you mentioned, of course, would be one option.
These suggestions will be more effective and do less harm, IMHO. If this is not sufficient, Rives specializes in calculating specific recommendations based on your dimensions, etc. Good luck!