I'm looking into getting a new monitor, possibly a 4K monitor, but likely just a 2560 x 1440 (WQHD) model. I like the specs of the new Dells (2715Q, 2715H, 2515H), but am particularly interested in the built-in USB 3.0 hubs, as I plan to use the monitor with a 2013 15" rMBP in clamshell mode. The newer Dells all appear to have same 1-up/5-down USB 3.0 hub, with one of the hubs having high-output (I'm assuming 2.1) charging capabilities. Can anyone with personal experience comment on how well the built-in USB 3.0 hubs work? One question I had is whether the four non-"high power" USB ports on the hub are still powered - i.e., could they power a bus-powered USB 3.0 external HD? Many thanks in advance.