The Cambridge Audio DACMagic XS Headphone Amp ($189) plugs into your PC or MAC via a USB connection and provides audio quality that will blow you away. It takes your current MP3s and high res audio files to an entirely new level. A USB 1.0 connection will support up to 24-bit/96kHz and a USB 2.0 will support up to 176.4kHz/192kHz. In order to get this resolution on a PC you’ll need to install an extra driver. The unit itself is small and made from esthetically pleasing aluminum. You be hard pressed to find a better bang for your buck.