If you make sure you uncheck "Resample" and then change the dpi to 300, it will give you print resolution with no actual change to the file itself. It's basically just telling the file, fit all these pixels into a 300dpi space instead of spreading them out over 72dpi. If you're scanning 4x5 (assuming here) then the X5 can give you about 2040 dpi. Here's what the file's dimension would look like in Photoshop at 72 dpi...



and here, if you change the DPI to 300 with "Resample" unchecked...



Note that the new inch dimensions have changed to reflect 300dpi and these are about the largest you can get out of an X5 scan of 4x5. Also, see how the image size and the dimension in pixels remains the same? This shows that you're not degrading (interpolating) the file with the dpi change. Make sense?