surround sound hookup
 

Trying to improve the fidelity of my winamp tunes via stereo system....

I currently route the line out of my Turtle Beach sound card into a Denon A/V receiver which sounds pretty good all and all when using Winamp to play my MP3s. I want to improve the fidelity, and it occurred to me (why didn't I think of it sooner) to just connect the digital output of the sound card to the digital input of my Denon receiver and let it take care of the PCM decoding. Is this the best connection for improving fidelity? Should I worry about the cable picking up noise - worth buying a monster cable?

If you want to improve fidelity then definitely go with the digital cable. Analogue signals are succeptible to interference - digital signals are not, for the simple reason that at least one form of error checking will be integrated with the digital signal.