What kind of speakers were those again?
Like the surrounds-hidden-in-the-plant idea, too. Hey, anything within reason to improve the WAF!
Seriously, only thing that gives me pause off the bat is the glass cabinet fronts right next to the mains and the speakers being right next to the cabinet; potential reflection and diffraction issues there IMO. Have you tried (or is it practical) to move the mains out a little further so they're a bit more forward of the cabinet (I see on second viewing that you already have them out a bit)? Maybe deadening the wall behind the speakers and/or the adjacent cabinet sides with some sound-absorbent fabric hangings or panels that aren't ugly would help, too.
Bet that rig shakes the room nicely!