There could be several issues and Realtek is subject to, and can cause problems.
The least likely is that your audio cable is not shielded very well and there may be something emitting a strong magnetic interference wave. Go buy well shielded audio cables.
2. If the front audio port on your case is low quality, the cable may not be properly seated in the MB pins.
3. Disable all other audio devices, especially the HDMI audio : Kill any obsolete audio / video codecs or running apps like quicktime. Just my opinion, this is why I do not use, or allow HDMI to carry an audio signal.
4. IF the performance is the same as listening to steaming audio as audio running an application, you have a software conflict. If not, You have a software conflict.
It is 99% unlikely that it is a hardware issue, but a conflict. Try running as many different audio file types as possible, burn a encode a CD into MP3, WMP, and other audio formats. If just one is fine, you have a conflict. If you can't troubleshoot it and have better quality out the back ports, sometimes you just do not notice it as much.
Buy a USB sound device.