Don't the products have manuals with explanations? Googling PM6005 subwoofer also turns up a lot. Some of the threads referring to the PM6003 also apply to the PM6005.
In short, as far as I can tell, because the PM6005 doesn't have pre-outs or a sub out, you need a subwoofer with high level (speaker type) connections, but the sub 8 doesn't have this type of connection. I don't think the recording out on the back of the Marantz can be used because it is probably fixed level (i.e. the volume won't change as you change the volume of the amp so it won't be in balance with the music,etc.).
That said, I haven't looked at the Marantz manual so that may provide more information.