Positioning costs nothing. Start there.

The first upgrade I recommend to anyone costs nothing. Move your speakers. Toe them in, toe them out, change the distance from the back wall and from the side walls, in very small increments.

When my B&W Diamonds made my room sound worse instead of better, this was step one, before a single panel went on a wall. On the Bowers it was quite simple: a little toe-in, a little toe-out, the distance from the wall and from the sides. You hear the differences pretty much immediately.

I know it is not always practical. Most of us listen in the living room, and a living room comes with restrictions that a dedicated room does not. Still, experimenting even in tiny steps costs nothing and can dramatically change the properties of your soundstage.

I put a number on it. Positioning done properly is worth the gap between a $5,000 pair of speakers and a $15,000 pair, and that is $10,000 of performance for nothing but patience. Keep moving them until the soundstage shows you the elements you were looking for, and only then think about panels.

Nobody sells you a toe-in angle. That is exactly why so few people bother to try one.