the max read is around 20Mbps on the cdj2000/nexus sd port. The reason being is because that is more then enough to send 4 lossless music files to 4 different cdjs. Now why you would want faster is for writing reasons. a SD card that writes faster will save you time at the computer when transferring songs from rekordbox to your SD. How much time do want to spend sitting at your computer waiting for songs to transfer? That's what you should be asking yourself when deciding how much to spend on a SD card. Hope this helped :)