My SVS1000Pro arrived, and given its relatively small sealed size for a 12" sub, this positioning on the heavy [Western Juniper] shelf sounds excellent as a 2.1 setup!
Proximity to the upstaris listening area also works - I'll see if I can configure a preset to add a bit of subwoofer gain when I'm listening in the loft (where the sub sits about 2' under the floor decking). I'll also put the SVS' grill on when I get around to better cable management

. The wire running down from above is Ethernet for the WiiM Ultra.