I would appreciate any thoughts about upsampling techniques to create the best possible prints from existing 5MP images on an Epson R2400. I realize of course that this is a "pixel stretch." The images are 2592 x 1944 (4/3), resulting in 150 PPI in the short (limiting) dimension.
In as much as print file resolution is generally much smaller than printer resolution (even under ideal circumstances when a ~340 PPI print file is sent to the printer), the printer driver itself may be thought of as performing an upsampling operation.
My main question is whether it is better to upsample in CS3 (e.g., "bicubic smoother"), to just send the 150 PPI file to the printer and let the driver do the upsampling, or some combination thereof. And, if it is better to upsample in CS3, at what point in the workflow is best? (I.e., should this be done before or after sharpening (which I believe is generally considered to be treated as the final step before printing), or somewhere earlier in the workflow?
Any other suggestions that could help with this resolution dilemma are most welcome.