Those Klipsch speakers at 98db sensitivity don't need much power at all. I have no experience with either of the Marantz units you mentioned, but I'd get the PM8006 if it's a choice between the two. It will have plenty of power and give you the flexibility to add other sources, you can connect a subwoofer to it, it has balance and tone controls, and you can add an amp to it in the future.