I too think you need to give these a long audition in your room, with your system and music before delving into mods/upgrades. once you have identified any shortcoming you can then focus resources on resolving that.
Looking back after my long history of tweaking I think the sound form a stock 1990´s k-horn is almost perfect. Of course, the speakers can be upgraded and/or optimized for your system and tastes. one of the great things about these speakers is how much tweaking can be done.
For the time being my advice is to get get them seated in corners and listen to the music! afterwards you can begin to look at the crossover, drivers, horns, etc.
warm regards, Tony
"Give me Klipschorns or give me death!"
Jean-Francois Lessard PP 2A3 Amp, Marantz 7T Preamp, 1993 Klipschorns with ALK xovers, Asus netbook running itunes and LMS serving Squeezebox Touch, MSB link DACIII, MSB digital director, Audioquest Diamondback ICs, Synergistic Research Alpha Quad Active Shield Speaker Cable