OK, I have these exact speakers hooked up to my desktop which lacks a 3D sound card meaning I have only one (stereo) output. The speaker system will come with a audio connection wire that has three inpts/outputs. There will be center/sub, rear, and front audio inputs/outputs. Do not worry though! The color scheme goes as follows:
All you will have to do is plug one of the green ends into your PowerBook's audio output then plug the other green end into the audio receiver, it is just that simple! You then have many options when selecting what type of effect your want your speakers to play. From a single stereo output you can have the effects of 6 Channel Direct (meaning it WILL BE STEREO), Stereo, Stereo X2 (meaning it will still have the stereo effect but it will use ALL the speakers), Pro-Logic II Music (it will emulate the stereo signal into a 5.1 surround sound output), Pro-Logic II Movie (it will emulate the stereo signal into a 5.1 surround sound output). You DO NOT NEED a 3D sound card to have 5.1 sound playing through these speakers. However, I highly recomend buying a external USB sound card to take advantage of Dolby digital surround sound.
You will be fine if you order these speakers as your PowerBook will hook up to them just fine without the need for extra equipment. You can hook up anything that has a headphone output such as a portable music device (such as an iPod or PSP), portable DVD player, portable CD player, ANY notebook or desktop computer, just about anything.