I sounds like you are moving towards a near-field set up. In this set up I found that you eliminate some reflection problems but you may loose some depth and fullness. Keep trying the suggestions that do not cost money. I threw up couch cushions, pillows and blankets all over the place to try and figure in out. As far as the stairways and computer desk, these are irregular surfaces that can diffuse the sound so that it does not bounce back in an undesirable way. I only know a little more than what you read in the link I gave you, but it makes sense if you think about the chambers that speaker designers use measure their designs, they want to remove all reflections to measure only the speaker's performance.