I'm not up to scratch with PC speaker offerings these days, but have you considered headphones? Great sound per pound...
Failing that, when I cam to this forum I asked almost exactly the same question. I then ended up purchasing a DAC, integrated amplifier and a pair of speakers! I bought the amp and speakers first, which came in at £300. Better quality than an equivalently priced 'computer speaker' set up like those offered by logitech etc etc.