After 130 hours of burn-in, my amps sound fantastic. What a difference from their out-of-the-box performance, where my initial, gut-retching reaction was that I had blown a voice coil. I did not chart the course of the burn in, but am thrilled with the 9V3SEs performance now. I moved from V1 to V3, so this is a little off the point of the thread: the 9V3SEs midrange is liquid, and the top end smooth and grain free. I, however, am not crazy about the impedance change. If you have not taken advantage of this upgrade, do it at your earliest convenience.
Mark