Run in time for an amp, IMO, is less than a few hours. Speakers on the other hand, are an electromechanical device, and WILL need running in. The run in time will vary greatly with the music you listen to, low volume chamber music won't work the drivers like loud thrash metal will. Another thing to consider with respect to the difference in highs between the two speakers is the aim of the high frequency drivers in reference to your ears in your seating position. High frequency drivers seem to have a smaller sweet spot, make sure they're aimed well, both vertical and horizontal planes are important.