[cosmicma]

what size will your final print be and what size is the image you want to print ?

the reality is the resolution of your image determines the size of print at a given DPI
an example would be if i had an image with a resolution of 3168 x 4752 and i wanted to print at 300dpi the print size would be 16" x 11" ( approx )
if i wanted to print an image with the same resolution at 10" x 8" the dpi would be closer to 500 DPI

the only way i can think of to get the desired DPI ( 300 ) is to increase the size of your image through interpolation ( pixel doubling )

another thing to keep in mind the larger the print the further away the viewing DPI resolution becomes less of an issue and depending on print size a lower DPI resolution is quite acceptable