The upgrade was around $100 total. The upgrade was for those who thought they were a little too forward and bright. According to Dennis, the highs were smoothed out and a flatter frequency response was achieved especially in the highs (with no sizzle introduced in the region above 10khz). These are not my words. This is how dennis explained it. I have had the pleasure of talking to him and he was very honest and straight forward. He even had me donate the charges for the mod to an orchestral organization. A class act.