Using a preamp to boost gain into the amplifier to make up for it's lack of power is not a great gain structure or system design. We need to know more about what is driving the amplifier to help.

If a multi-channel amplifier has been spec'd, I have to assume there is a multi-zone switcher or source behind it. That switcher or source will be capable of outputting a -10dbV signal when turned up all the way. That is as high as a line level signal should go in the consumer electronics world. That is as high as the amplifier ever expects to see. Although you can boost that signal, doing so will increase distortion and is almost guaranteed to clip the amplifier. Which as we all know, is how you blow speakers.

I can't imagine a scenario where the outputs of the 12ch Episode amp don't have enough power, assuming this is a house or light commercial environment, you are using traditional switching/source components, traditional 4-8 ohm speakers, and everything is connected properly.