Welcome. Rob Galbraith's site (http://www.robgalbraith.com/bins/index.asp) is probably the best reference for camera/card write speed info. However, the chart for the D300(s) is no longer up. If I remember, however, the camera's fastest write to card speed was 30MB/s, with the fastest available card at the time he did the testing. Any advantage gained by using the faster card would be downloading to the computer with a card reader.