I would recommend a cable that adapts from RCA male(hooks to stereo) to 3.5mm male(plugs to sound out of PC) if you don't use a sound card with RCA outputs. I have a 3 meter cable that has RCA on one end and 3.5mm on the other. You will not lose quality of audio with a quality cable, and less connections (like the adapter above with female RCAs) means less chance of loose plugs and loss of signal.
Creative's Titanium HD is an awesome card that does have RCA outs also. It is working beautifully for me, and I also play older games so the EAX capability is fantastic to have work right. Asus's implementation does lack in proper EAX support.
The Ti HD plays music like you won't believe. I have heard nuances in songs I have listened to for over 25 years that I never knew existed. Well worth the cost for clean audio in my opinion.