Hello Dan,
I don't see any reason why that wouldn't work. Although, you may want to plumb extentions for the Rio pump to be submerged and on the return to reduce noise. Even better would be to feed water directly to the aquafuge right from the drain from your display tank plumed with a ball or gate valve so you can move water through it more slowly and cap your feed from the Rio pump. If you decide to use the aquafuge under it's own power just make sure the rio will deliver enough flow for your needs depending on the water level in your sump. I personally don't know if the pump that comes with the aquafuge can handle any head pressure or not so you might want to test that out. I'm sure a Maxi-jet would give you all the pressure you'd need. Hope this helps you out some and please let me know how you like the aquafuge, I've been thinking about trying them on some of my Clients tanks.
Myk.