[cclesue]

In all this (I might have missed it) I see no discussion of the raster function. Rasterization is what the computer and/or presentation device (monitor, printer) does to the input file to prepare such for presentation. Raster engines are resampling programs that take the information given them and spreads in out over the specified area. If there is enough information it might drop some of it or if not it will fill in the gaps by averaging from pixel to pixel. These raster engines are built into graphics cards and printers and to some extent monitors and they don't give a damn about DPI, PPI, LPI. etc of the input file. All they care about is how much info is given them and how thick or thin do they have to spread it. The only control the human element has in this is how big an input file and what are the final dimensions of the output. In other words assume you want an 8x10 print from your Printer (be it your personal Epson or the Noritsu at Costco's). You have a 6 meg file (2000x3000). You input this file and the raster engine takes the information and "fits" it to the desired output. In this case the engine will spread the 3000 pixels (the long side) over the entire long side of the paper. Ah ha you say that works out to 300 dpi or ppi. . . but to doesn't because the Epson was set to 720 dpi or 1440 dpi or the Noritsu is 320 or perhaps 280 dpi or the monitor is something else. In other words the raster engine DOESN'T CARE about all the work you did to prepare the file for output. All it cares about is how big do you want it and how much information does it have to work with. Obviously if it has more information to work with it will produce a better product, too little and the output will be lacking.
Having said all this there is one point that needs to be considered. Just how good is the raster engine of the output device and can anything you do improve things. The resampling engine in photoshop is pretty darn good but frankly speaking every time you fiddle with the information something is lost in the translation so the best thing you can do is don’t do it until the very last and only then if you either don’t trust the rasterizer in the output device or you are concerned about file size. For the most part the Raster Engine in the big pro printers is superior to the PS engine, but the one in the cheap HP and Epsons might be lacking. When cropping (in PS) set the size but leave the resolution field blank this will prevent the PS resampling engine from kicking in. We send our files to a Noritsu without resampling and the output is great. Finally if you MUST resample pick a dpi that is a derivitive of the output device. If your printer is set to 720 or 1440 then resample to 360 dpi or 240 dpi. I doubt the naked eye can tell the difference.