My SD card reader just plugs into USB, it might actually be usb3.0. I know I can just buy pcie USB expansion board and get an extension cable but I have all these unused 5.25" drive bays that I'd love to throw a card reader with maybe a few more front USB ports into. It would just a a cleaner look, and have that retro 90s gaming pc cred of putting random shit in drive bay slots.