Need to improve sound on desktop

I'm very unhappy with the sound from my Sabertooth motherboard and need advice as to what sound card to buy. I have been away from computer audio for years now. What's a good sound card to get? Budget? Hmm, $100 but if its that good I can certainly go up. Is eBay safe for a used card? Any other idea as to how to improve the sound is appreciated.
You may be better off going with an entry level DAC. Something like an AQ Dragonfly should work very well for you.
The jitter of the digital source is critical, more important than any other thing in a digital system. What you are experiencing is jitter. This can be reduced with a reclocker such as the Synchro-Mesh, but the cost is $600.

You are probably also using something like iTunes on a PC. Never do this.

On PC, you should be ripping CDs with dbpoweramp to .wav files and playing back with either Foobar2000 with Kernel Streaming or JRiver. Both of these are even better used with Jplay.

PCI cards all have relatively high jitter, even the $2K ones.

Steve N.
Empirical Audio
My desktop is not hooked up to my stereo. I listen to some music but it is mostly podcasts and games that sound muffled thru my Monsoon speakers compared to my previous computer. I want to continue using the Monsoon for now.
I just looked up the AQ Dragonfly. That looks like an interesting alternative. Steve, I'm familiar with Foobar even though i'm not using it right now. Thanks guys.