Setup Speakers Along Long Wall?

Nice system. A great looking room.

Looking at your system my guess is the subwoofers are overloading the room with bass. I assume with the subs turned off you do not have the problem with the turntable? I would start here. 
 

I am fortunate to have a large room. As @curiousjim points out, having wide spaces on both sides of the speakers can be good. You’ll probably need to heavily dampen  the front and  rear walls and the ceiling. It is worth a try… but I would first figure out how to stop the feedback. 
 

I’ll give it some more thought. I am sure with the additional info you supplied, there will be some folks that will have helpful suggestions.

If it were me in that space, I'd still try and utilize a short wall setup. It's a nice looking room with nice gear. I would first try a wall shelf to the side of the window for the TT, as it would be behind the speakers and possibly help with isolation from the floor, which is obviously suspended. If that still proved troublesome I'd look into isolation tables, to put on the wall shelf under the tt, from basic passive units, to high dollar active. Additionally, I'd really limit the subwoofer setting, place them outboard the speaker stands for space, and move the rest of the equipment low against the wall under the window. I see you've got some treatments, which is a good thing, many people overlook this crucial detail. I'd hazard to guess the interactions with the turntable are from the floor and not airborne, but I could be wrong there. You'll just have to try Jenga a bit moving stuff around to get the best compromise. 

I don't have cartridge feedback with turntable located as in picture.  I talked to the Wilson people and they prefer the speaker location as is, so I'm looking for a preamp with balanced out and 3 meter XLR interconnects.  My dealer suggested Whest, or Rega Aura and Wilson dealer suggested baby Boulder.  More bass traps on the way.

Go long young man!

Just looked at your setup. Nice equipment! After looking again at the picture, I would definitely cover the window with something and after your bass traps come, take a couple of those absorbers and place them on the ceiling above the speakers. Maybe a bookshelf or two or something on the right wall? 

Did you do any calibration when you setup the Subs in the new room?

All the best.

JD