When I upgraded my system to Klipsch, I was astounded at how much better everything sounded, with a high grade center speaker. I have a 7.1. I'd say center is most important, then sub, then the two fronts (which would not be bookshelf if at all possible). Other 4 are smaller hang on the wall types. You certainly do not want front and side/rear the same speakers, unless you plan to one day upgrade the fronts to better speakers, and use what you've got in a 7.1 system.