Boomy and echo'y isn't going to be fixed by EQ. The room needs to be treated. Most likely, the overabundance of bass reverberation is giving the impression of reduced highs. The Klipsch are anything but laid back in the top end - especially with them pointed right at you.
Leave the chair in the room. Try moving the seating to get things the best you can from a frequency response standpoint first (no EQ). Treatments are available for stand mounting or floorstanding that would require no mounting holes.
Blinds without curtains all behind the speakers isn't helping anything either as you're likely getting lumpy bottom end due to speaker/wall proximity.
Lastly, it's a square room. This means that all of the bass modal issues are going to pile right on top of each other. Get in the best place you can. Start with the seating about 6.5' back from the front wall to your ears. If you're against the wall, you're fighting a losing battle unless you heavily treat the wall behind you and even then, you'll have some issues.
Bryan