Unlike the previous Fiio E10 USB DAC where installation was literally plug-and-play, my experience with Audioengine D1 is quite challenging.
Issue 1 - only USB 2.0 ports can be used in my Asrock z68 Extreme4 motherboard. USB 3.0 ports are no good.
Issue 2 - USB cable length should be 1m or below. If a longer cable is connected to a USB 3.0 port, Windows 8 reports an unknown device. In a USB 2.0 port, Windows 8 reports good Audioengine D1 installation but audio performance is NONE (only quick beeps or buzz).
Issue 3 - my Audioengine A2 speakers sit on my desk but my PC is on a shelf around 1m above. My oxygen-free RCA cables are only 0.75m long.
Fortunately, I have an unused 2m Toslink cable lying around. So using a 3m USB cable (for D1 power) and this Toslink cable (for D1 audio source), I found a setup that satisfies my needs.
In Windows 8, S/PDIF is set as Default Playback Device while Audioengine D1 USB is automatically set as Default Communications Device. I set S/PDIF to 2-channel, 24 bit, 192000 Hz. Note that if I opt to use USB only, maximum setting would 'only' be 2-channel, 24 bit, 96000 Hz.
To be honest, I couldn't tell the audio quality difference between USB and S/PDIF as digital carriers. If I could use a 3m USB cable, I would have chosen USB for simple cabling.
In summary, if you want to use a longer USB cable (say, 3m), then also use a Toslink cable to carry digital audio data.
Update: one thing I don't like with D1 is that the analog RCA output is variable. I prefer it to be fixed as I primarily use volume control in my powered speakers. FiiO E10 analog output is fixed; only the output for headphone is variable. However, with E10, even with a headphone plugged in, analog output remains active. With D1, analog output switches off when a headphone is plugged in.