mdfoy,
Okay, let's work the problem. I am going to assume for now, that the listening position and speaker configuration is set up as is and there is little if any chance in changing it or moving it dramatically (i.e. a different room or a completely different area in the room you have them in). In addition, I am going to assume that reconstruction of this room is impossible, i.e. removing the two vertical pillars.
I would begin by treating your first reflection points.
The closest one you have is likely the ceiling. I would draw a line from the main listening position (MLP) to each speaker. The midpoint of that line, on the ceiling is where you should place a GIK 244 or equivalent 4 inch to 6 inch absorber. Do that for each speaker. Next I would place one or two GIK 244's (depending on how many will fit) on the ceiling over the MLP, to act as a 'cloud' absorber. Next, I would place a GIK Monster Trap behind the listening position (either 1 or 2 next to each other) on the door behind the MLP. Then, I would install 2 or 3 GIK 244's or Monster traps on the front wall between the speakers.
I would remove the coffee table, since it is probably at a reflection point on the floor (it is the same reflection point on the ceiling as described above). Carpet or a throw rug should be sufficient for the floor.
In order to minimize both the visual and acoustical deterrent that the two vertical pillars may cause I would move the MLP a little closer and turn the lights down. That's up to you though.
Some other advice:
You have speakers that are very sensitive (99 dB), are ported in the rear, and are attempting to control directivity which is a good thing. From an acoustical standpoint, you essentially do not have side walls, they are very far away. I would recommend a preamp that is only about 3-6dB gain and a power amp with lower gain and lower power as well which should render a system that has a lower noise floor and hence more detail. Your preamp is about 15dB gain. Your power amp is at least 100 watts and about 26dB gain if I recall. With the speakers that you have, you really do not need more than 10-20 watts even when you are cranking it to 100dB SPL. You already have a phonostage I am assuming so you should be getting enough gain from there to satisfy your vinyl playback. Your digital source has an output of 2V RMS which is standard and will work fine with a highly sensitive speaker (99dB!) as long as your preamp gain and amplifier gain isn't too high, hence my advice.
If you do not like the looks of the GIK 244's you can always use the Alpha series or Impression series and get similar performance but a better look. Or you can use Art Panels which are just decorated print versions but more expensive. You can discuss that directly with GIK.
Read about 1st reflection points on the GIK website and/or RealTraps website. Ethan Winer had some nice diagrams on the RealTraps website.
I would consider the above first, before considering any pure diffusion panels which should be implemented, carefully.
Good luck,
Best,
Anand.
