Danny Ritchie offers upgraded crossovers for the RS750 speakers as well as some other models. He also recommends using some of his No Rez foam along the ledge that overhangs the top front of the speaker. The foam in question is on the left in this photo: (the other is Black Hole 5) Anyone use the foam or the crossovers? Any comments on effectiveness? Anyone know exactly how the foam is cut/shaped before application? In other words, what does the tweak actually look like when applied to the speaker?