Help using Nik Sharpener Pro for output to Aperture Book...

I wonder if anyone knows what printers Apple uses in the U.S. for Aperture book printing. 'Googling' leads me to think that they are 'digital' but I don't know how to translate that for the settings in Sharpener Pro.

Or is there a prescribed way to sharpen (with general setting info) in Aperture itself. I know how to sharpen in Aperture (3.4.3) but don't know what is the right method for images destined for a book.

My images are almost all portraits, and close-ups specifically, so eyes are particularly important.

I have spent a lot of time trying to find help with this online. My two Aperture books say nothing.

Any other advice for optimizing the results would be most appreciated.

Thanks...