I think there is a fatal flaw in trying to get good sound from this system, apart from the sonic's of the equipment which I agree may not approach optimum.
The OP sez that the speakers are 5ft apart and he listens to them from 12 feet back. The speakers are only 2ft off the back wall and are not symmetrical to any of the walls in his 18x18x9ft room, not good room dimensions as we all know, and the excessive nulls and nodes which will defy correction, will all be too apparent. The room will have more reflections than just the important 1st reflections to deal with. But with a lot of work via experimentation with set up he should be able to get something reasonable.
The OP complains of harshness which could be from excessive 1st and 2nd reflections off the walls, as well as reflections off the ceiling. He wants more 'air' but in my humble opinion he hasn't even approached the height/width sound stage available let alone the sense of depth and 'air'. In fact even if he is listening in a triangulated seat/speaker placement, he still isn't getting much more than expanded mono and the attendant congestion caused by having speakers too close together.
IMHO the OP need to think out side the box by discarding for the moment what won't practically or esthetically work for him and play with setting the speakers up in a classic manner (starting with the Cardas methodology) and also set his system up in a very near-field set up well away from the boundries to see what his system really sounds like without room boundary reinforcement and reflections. He should also be mindful of the benefits of proper toe in used to minimize 1st reflections as well as optimize speaker focus without getting a hot treble (which depends on the speakers driver's designs on and off axis.
He should also realize that, as he has already been told, there is no cure for his problem without a lot of experimentation. You can't buy what he needs other than some good books on all things audio, especially rooms, set up, and managing reflections appropriately.
FWIW.
The OP sez that the speakers are 5ft apart and he listens to them from 12 feet back. The speakers are only 2ft off the back wall and are not symmetrical to any of the walls in his 18x18x9ft room, not good room dimensions as we all know, and the excessive nulls and nodes which will defy correction, will all be too apparent. The room will have more reflections than just the important 1st reflections to deal with. But with a lot of work via experimentation with set up he should be able to get something reasonable.
The OP complains of harshness which could be from excessive 1st and 2nd reflections off the walls, as well as reflections off the ceiling. He wants more 'air' but in my humble opinion he hasn't even approached the height/width sound stage available let alone the sense of depth and 'air'. In fact even if he is listening in a triangulated seat/speaker placement, he still isn't getting much more than expanded mono and the attendant congestion caused by having speakers too close together.
IMHO the OP need to think out side the box by discarding for the moment what won't practically or esthetically work for him and play with setting the speakers up in a classic manner (starting with the Cardas methodology) and also set his system up in a very near-field set up well away from the boundries to see what his system really sounds like without room boundary reinforcement and reflections. He should also be mindful of the benefits of proper toe in used to minimize 1st reflections as well as optimize speaker focus without getting a hot treble (which depends on the speakers driver's designs on and off axis.
He should also realize that, as he has already been told, there is no cure for his problem without a lot of experimentation. You can't buy what he needs other than some good books on all things audio, especially rooms, set up, and managing reflections appropriately.
FWIW.