What do you use for dac/amp and music source with the HD58X’s? You may want to look there first, for improvement, having sufficient power headroom floats all frequencies. You will likely bring more out if your 58X’s if there is room for improvement on that side. You would also be prepped to try different headphones, that will likely need more driving power to perform their best. The DAC really is important, as well as the final frontier, the source of your music.