Adding an external DAC will produce results in most cases. As an added bonus you can plug in other digital sources such as DVD player, FreeView box, etc into a DAC and enjoy a big gain in quality.
Highly acclaimed M-Audio Super DAC 2496 is only about £150 now new and around £100 used.
It is made for the music industry. A much bigger market place than stereo hi-fi. Economies of scale that mass production brings keeps the price down to levels hi-fi industry can only dream of. If it is a 'hi-fi product' sold though the hi-fi trade with its big margins, it will have a 'hi-fi price tag' of at least double.
For specs and features see data sheet at http://www.gbaudio.co.uk/data/dac2496.htm