Okay, not knowing how you will use the audio device, I suggest for music/games/monitoring:
DacPort LX if you don't need a built-in headphone amplifier, or
DacPort, if you need that built-in headphone amplifier.
See
http://centrance.com/products/
Otherwise, for a little less money, you can try the DragonFly.
See
http://www.audioquest.com/usb_digital_analog_converter/dragonfly-dac
All of the above are USB, and I personally love the DacPort, cleanest sound I have ever heard.
If you want to get something a little more economical, you can try the ODAC by nwavguy. I have two of those, and they are also super clean. You can get a fully assembled one for about 150 bucks or less, depending on where you get it. You can also get a ODAC+O2 headphone amplifier in one chasis.
See for example
http://www.jdslabs.com/storecat.php?fetchcat=5
I have both the O2+ODAC and ODAC stand alone, as well as the DacPort, I have to say, they are all terrific. I built my own O2's, so I saved quite a bit of money with spare parts and PCBs left over should I want to build more.
PS. I would recommend an external sound device if only because the internal components becomes obsoleted quickly when interface specifications change.