Could a speaker attenuator substitute for a preamp

I have four speakers. A pair of Klipschorns in the front corners and a pair of LaScalas in the center. I have one stereo amplifier, and one preamplifier to power and control all four speakers. The left channel signal goes to one K-horn and one LaScala. The same goes for the right side.In order to control the K-horns separately from the LaScalas, I will need another stereo amplifier, and another preamplifier. However, I could make small independent changes in all of the speakers by using post amplifier step attenuators at each speaker. I heard that post amplifier volume controls are a no-no. Are there any post amplifier step attenuators that are as good as class "AA" preamplifiers? I hoping that I won't have to buy another amplifier and preamplifier.