Here is the install finished. The 2 USB ports are on the right close to the passenger seat. It is nice to get rid of some loose wires on the dash. As you see I have enough stuff already. As for the USB's current draw, they are connected to the 2 USB ports on my DNX692. One provides 0.5 amps and the other 1.0 amps. I don't believe that there is any draw when the deck is off.
The wireless dongle works great. No need to connect a wire to the phone to display it on the deck screen anymore. The only bad thing was I had to order it from the UK. That made it a little more pricey but that's ok. The dongle is to the left of the console just behind my commercial radio. I had to leave it accessible because there is a reset button on it and it's not like I can hop out of my wheelchair to get under the dash to push it if need be.
Anyway I hope this helps.