Please don't shove your speakers up against your credenza and stick the subwoofer in the corner (I guess people think it looks good, or clean, or this is just "how it's supposed to look"? Not sure).

What you want is soundstage and stereo separation. So, unless I'm being photo-deceived by how far away your listening position is, you should move the speakers away from each other until you have an equilateral triangle between each of them and you, or, as far apart as you can get them if you can't quite get a perfect triangle (See? And you thought you'd never need geometry! Ha!)

Also you might end up toeing them in a bit depending on the imaging. Then put the subwoofer wherever it gives you the best response (no matter whether it's square to something else, or not exactly evenly spaced or whatever! you're looking for good sound, not symmetry).