I honestly don't know in this situation. This box has the sub amplifier in the box and the sub is passive. That means that the crossover frequency is fixed in the box and is tuned for the sub.
Since the impedance is the same, all I can say is try it. Speaker sensitivity may trip you up. If the new speaker is less sensitive, you would need to run it at higher levels. You would start to hear distortion and could potentially damage the amplifier in the box.
My advice is to experiment, but be careful. Increase volume levels gently and be aware when distortion starts happening.