Take a picture of your wall behind you and your side walls. Post that as well. Bear in mind that your current speakers are not dipoles, they are monopoles through and through. So although treating your front wall is a 'good idea', there may be other walls you should treat first, depending on the polar response of your speaker above 250Hz and below 250Hz. Are those B&W's? Which model?
Also, please list what treatments you already have up in some detail and which wall it is on. List all the walls, i.e. Front wall, rear wall, side front, side rear, floor and ceiling. It's hard to tell if you have GIK 244's or Monsters, etc...in the photo.
Best,
Anand.