Are you looking to upgrade an equalizer or an active crossover (XO)?
Per the Sanders Sound System website they appear to supply a DBX Venue360 DSP unit with their Model 10 electrostatic speaker. You will not be able to find an analog crossover that can do what the Venue360 can do. If you want to upgrade the Venue360 the only options that I am aware of would be one of the XTA DP 400 series models or the Meyer Sound, Galileo Galaxy. Some guys may come along and recommend the Xilica XP platform, but they are no longer in production.