Calibration, printing, and AirPrint

So, I completely understand the need to calibrate the display of my computer(s), in fact, I'd welcome any input as to the best reasonably priced calibration hardware for use with multiple macs/iMacs ;o). I can see how this would result in darker images when printing from Aperture to our Epson Artisan 730 printer.

That said, I am also seeing much darker prints when printing from the iPhone or iPod using AirPrint. It's not clear to me why I would see the same kind of darkened print from a completely different device with a completely different screen. This is making me wonder if there is something inherent to the Epson Printer that is causing the darker prints.

In case it matters, the prints from the Epson are incredible, just darker than they appear on the phone or computer. I realize this is an Apple forum, not an Epson forum, but y'all know your stuff ;o)

Thanks!