Neil makes a good point.
The cheapest way to make your system sound better is to have a stiff whisky.
Works every time, I think. Pretty sure.
But seriously, CDs ripped to Apple Lossless format, playing via a Macbook connected to a Benchmark DAC1 USB works pretty well for me. As an added bonus my iPod Touch then acts as a remote control, complete with album art and everything (using the free, imaginatively named 'Remote' app to get the Touch to talk to the Macbook on an ad hoc wi-fi network - i.e. it doesn't need to be connected to a router or an Internet or anything).
Of course, it also helps to have an amp at the end of all this, that has some glass in it. Which, interestingly, is the same material that whisky usually comes in.
So in summary, glass will make everything sound better, whether there's whisky or electrons in the glass.
2c