I am mostly sure that it doesnt work that way, as far as i know you have to export your music to an USB drive or hardrive to use it with the players directly and the USB connection is for interfacing the players as controllers in order to use them with DVS software.
The only players you can connect to rekordbox directly are the CDJ 2000 and 900 and these players have ethernet ports so you can make a ProDJ link between the computer and all the players through a hub or a DJM 2000
Rekordbox is a DB management software and not a DVS like Traktor and yes you can use them as souncards (i think because you can do that with the 400s) and use the players as controllers
You have to install the pioneer drivers and of course have an actual DVS software