If the active crossover you speak of is the DX-38 then yes, it has an input impedance of 20k. Think of the thevenin equivalent for the circuit. The output impedance of the CD player is <10 ohms, lets say 10. His CD player puts out 2Vrms I believe he said so plug the numbers into the voltage divider equation;
2(20000/20010)=1.99Vrms
That's the benefit of an active crossover, they are much easier to drive So clearly there is no impedance mismatch. Also in the DX38 manual it states that with a nominal input voltage of 1.55V it will put out a nominal 1.55V, it has unity gain up until you drive it with more than 8.7V then it will attenuate and keep the output voltage at a max 8.7V.
A 10 ohm output impedance driving a 20k ohm input impedance is not an impedance mismatch? It most certainly is. This is exactly how all line level audio equipment operates. A relatively low output impedance drives a relatively high input impedance allowing almost the entire output signal VOLTAGE to be delivered to the input as your equation demonstrates.