Sabai, Sorry, I must have missed your post from the 14th. I've been asked this before, and I am at a loss to put my finger on how to describe the sonic difference these make. The best I can do, is tell you that these substantially increase the "rightness." When they are turned off, somehow things just aren't right. I know that is not very satisfactory, but that is the best I can do. I have 3 standard PEAs, which were added one at a time. This may be a good way for most people to go. I got one at retail and bought 2 used from other AG members, so this was a very cost effective tweak.