I agree with etsuko, scanning may help. I've done this with my scanner a couple of times at high dpi mode, but just to save the trouble, printing 640x480 to 4R is fine!

You have a monitor displaying at 800x600, and 640x480 takes three quarter of your screen, what do you get? A size close to or bigger than 4R, and they look alright for the average human eye.

Don't look too close to the printouts and you'll be fine!