Right toe...Speaker placement in a room carries a lot of weight. Almost more than anything else. The room itself a very close 2nd. (Sometimes dominant in gross cases of reflections and standing waves though.)
You can alter the distance from walls and corners while keeping the proper array angles and orientation between speakers. And then the sub calibration as mentioned. Do any and all of that before touching any eq!
You can spend stupid money on all kinds of things with not much to show for the results. Moving a couple speakers 12" could solve all kinds of issues and make a big impact.
I know this was supposed to be about the sub. Just sayin.
Got my Sub in the front left corner of the room and always felt it's a great place for it.
Last night watched an odd little claymation movie called "Early Man" that had one scene with a faux Mastodon walking that was shaking the room before I even knew what it was (to great effect!)
Also, my front left speaker, at one time was sitting just to the left of a gas fireplace glass door, and I knew something wasn't right because my phantom center was shifted too far left, which by just moving the speaker another 6-12" corrected it back to center. (I blame Mrs. Pupster for moving things around out of her ignorance of the matter!)