@jackd: And, all the Rythmik's have what @mike_in_nc wants: a continuously-variable phase control, providing anywhere from 0 degrees of phase "lag" (no delay) to 180 degrees (16 milliseconds of delay, which does electronically what moving your sub back 16 feet does).
And @jackd, Rythmik's Brian Ding himself prefers and recommends line-level hookup over high-level, though as I said above he does provide high-level provisions in his non-XLR model plate amps.