What about the B&C 10HPL64 as a possible substitute for the Delta 10? Qts, Vas, and Fs are nearly the same, but it has better Xmax and BL. I guess I'm looking for a driver that will have reasonable HF extention to allow a 2kHz crossover, instead of 1200 or 1600Hz. I have a particular HF section in mind using a 2Khz horn.