How can I get the best possible sound from my PC?

I listen to internet radio. The better 128 kb/s streams are probably as good as FM (what is your opinion, by the way). My bottleneck is the PC. I have decided to use an external DAC (CIA for the office and Musical Fidelity at home). I am also using high quality digital cables (Kimber D-60 and Kimber Select). How can I put the best possible digital signal on the wire? The digital cables alone cost about $1200. So it would make sense to spend some money on the digital signal if it makes a difference. Any advice?

Thanks,
Ali