Hi,
I have a similar situation in an 18x21 room with vaulted ceiling. There is even some slap echo that remains. This was a problem untill I picked up a pair of the FJ Om Loudspeakers. The omni type design and sealed cabinet design seems to work well in this type of room. Very musical and easy to place as indicated in the 6moons review.
I picked up a pair of the Duevel Venus loudspeakers at a terrific price thus the reason for my being on sale.I can't afford both.Not that far over your budget.
I find a good omni very non fatiguing to listen to and appears to be more room friendly.
A friend has the Om Walsh model1(I think) and loves them.
Good luck,
Art