I did a lot of research on this and found as stated above if your forged then sure take the plunge however if you have a stock short block chances are it wont hold it for long. So yes it will make more power throughout the rpm range but make sure your motor can take it. This issue is partially what pushed me to begin my forged stroker build a couple months ago.
Edit: although if you're going to send it back to ATI for a rebuild anyway I would definitely do the upgrade to a D1SC-1. I sent my P1SC-1 back last year and didn't do the upgrade and kicked myself in the ass later on. I think it was only like another $500 or so for the upgrade and if nothing else you can pulley it back to keep the boost lower but still make more power throughout the rpm range.