Before you get started, you should understand that following the right advice here is critical. You can avoid a lot of work re-ripping your CD's later. The ripper and the playback software is critical to getting good sound quality. Depending on whether you are using PC or Mac, here are some tips:
The other important aspect of digital audio is that the MASTER CLOCK is the most important part. This is buried inside your CD player and also inside any computer audio interface that you use, including USB to S/PDIF converters, AppleTV, Airport Express, Sonos, Squeezebox Touch, Roku and others. The quality of this clock or clocks makes or breaks the audio quality. If you want it to match or beat the quality of your CD player, then dont spare the expense on the computer interface with the master clock in it.
If you just want a taste of what computer audio can do, and dont want to spend much, then get the Logitech Touch. This has a half-way decent clock.