There’s a move underway that will change your perception of music quality when played back from computers via USB. Some of these new items are small and inexpensive, but the effect they have is quite dramatic.
Without getting too technical about it, asynchronous DACs improve the way the data stream is buffered and re-clocked on its way out of the USB socket of the computer and before it hits the main DAC stage, and the result is sound quality that can rival other sources. Computers are electronically very noisy, with all sorts of digital processes causing radiation, and stray voltages skating around the physical environment too. There are also variations in the rate at which data is spat out via the USB, and this is a critical area as jitter is increased by these speed variations. Asynchronous DACs overcome this by regulating the data flow using their own clock and large buffer, thereby keeping jitter to an absolute minimum. 
The really good news is that these asynchronous devices are not all expensive, starting at an unbelievable $199 for this Musical Fidelity V-Link, which can be added to any existing DAC to improve its USB/computer source performance. Like the rest of the V Series, the V-Link is built into a minimalist chassis, with no extra expense lavished on cosmetics. There's not even a front panel, having input on one end (USB) and output on the other - coaxial and optical. The circuitry inside is of the highest standard possible in this format, and benefits from Musical Fidelity's vast experience with quality DACs and CD players.

HiFi World magazine summed it up as follows: "The device works superbly. There’s a clear sonic improvement compared to porting the signal out via USB to a non-synchronous Musical Fidelity V-DAC. Via my MacBook Pro, the V-Link feeding the V-DAC made for a smoother sound, with things in better focus, and a superior sense of ease and flow."

Even if you don't have a separate DAC, you could use this device to improve the performance of computer-based music by routing it through the V-Link then into a digital input on your existing gear, such as a CD player with coaxial inputto its DAC (Marantz do this is some cases), or your surround receiver. It is potentially a very cost-effective modification to many systems.