Have you tried putting nothing, zero, zilch between the speakers? That made a huge difference for me with my speakers 30" from the front wall. I had my tweeters 45" from the side walls. Huge soundstage side to side and top to bottom. Depth of soundstage was pretty good...but I've heard better (speakers were 12' from the front wall).
Soundstage
I have a decent size room 20’x33’x9’. Due to the placement of some large columns I need to place my equipment on the long wall. While I can achieve an equilateral triangle between seat and speakers (11’ on all sides) .... I am unable to have the front of the speakers more than 3’ from the front wall. I am using Avantgarde Uno speakers with Pass Labs XA 60.8 amp and AR Ref 6 pre. Sources are Lumin X1 and SME 20. The overall sound and imaging are wonderful. There are two problems that I can’t seem to get right. First, the soundstage is rather narrow ... does extend beyond the speakers (have tried every off to on axis position). Second, the image is detailed/precise but not deep ... it just sort of hangs on the wall 3’ behind the face of the speakers. I believe that the problems are due the speakers not being far enough from the front wall but I can’t move them out more (due to the columns I mention). Any suggestions on how I might fix these two problems?