USB spec limits cable length to 5m for highspeed devices. It also limits you to 5 hubs deep on a connection. I need to go something like 7m or so, from a hub to a hub. So, computer to hub-right-next-to-it to hub-in-next-corner to final-hub. Easy, right? The first and last hubs are powered. Does the middle hub need to be powered, or can I get one of those 'cheap' unpowered things they sell for laptops, just to be a relay in the corner?