What can I power with this plate amp?

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I have a plate amplifier from a polk audio dsw micro pro 4000 home sub. I once owned one and had some problems with it so the sub went back but i got to keep the working plate amp. Since the amp is proprietary to polk there are not many specs available. according to polk it's 1200 rms. Not that I need another project or another home sub but would like to make use of this amp.

http://www.polkaudio.com/products/dswmicropro4000

Still reading on transmission lines but i know that i want to build one. Either way the problems i have are, what impedance to choose and how much power do i really have here? The only thing i know is what polk says and that the sub was around 6.5 ohms measured by me.