Think I'm going to purchase some Harman Kardon SoundSticks II for my Mac Pro. I currently have some good headphones and use the front jack. How do I hook up the three speakers? Do they all plug into one jack in the back? And what about the subwoofer, does it need a special jack. Final question: is there something I could purchase to improve the sound that wouldn't be too expensive? I.e. is there some USB extension or sound jack item that I can buy, which will improve sound performance, and plug the speakers into that? Don't know anything about computer sound or USB and sound, hence this question is noob.