If you are serious about printing from Aperture, or from any software, the single most important thing you can do to enhance the quality of your prints is to invest in a hardware display calibrator. It used to be the case that calibration hardware cost hundreds of dollars, but today a good display calibrator can be bought for around $100. While you don't strictly need a display calibrator to print, there are numerous advantages of having one. To understand why it's important, let's take a very quick look at the underlying technology, ColorSync, and how it affects your printing.
The problem with imaging technology is that all color is not created equal. Every device you own sees, displays, or outputs color slightly differently. You have undoubtedly had the problem where you tried to print something, but the colors on the print looked completely different from the colors on the screen. To get around this problem Apple developed a technology called ColorSync. You have...