The most cost effective change was to readjust the positioning of my speakers. All it cost was my time and a bit of trouble. I have been concerned about the room acoustics for years, but there has been little that I can do in an apartment. However, I am careful about making sure that wall decorations and furniture is appropriately situated (which, by they way, is typically visually pleasing as well), and that the system is as well situated as possible (my wife thought it odd at first that my ideas for arranging the living room were completely based upon what was best for our system, but when I explained why everything should be where it should be, she was fine with it; she likes good sound, too). I have heard good systems sound dreadful in other people's places, where they have not bothered to put anything in the room to absorb the sound, and they get a horrible echo. They might as well listen to something cheap, because their system isn't going to sound any good unless they fix their room problems. I also use a test disc and sound level meter to balance the channels, but that made very little difference, as my adjustments by ear were very close to what I ended up with. As an aside, the test disc for my picture adjustments made little difference, too, because they were very close to what I did before (I have always liked natural looking colors and such). But they both improved things, and were inexpensive. Buying Aurum Cantus Leisure 2SE speakers made a big difference, but they cost a bit of money.