Given that you have a computer with a big hard drive and lots of iTunes, your suggestion of using your computer as a source is a good thought. For only a couple hundred you can buy a Squeezebox and, along with your computer, you've got a pretty good source. For a budget amp, a used NAD or Rotel amp or receiver would be good. For inexpensive speakers, you will get as many recommendations as posters, but I've always liked PSB as good value for not a lot of money.