For sale is a Gustard X20u with USB. See the glowing reviews on Head-Fi, What's Best Forum, and other places. The DAC is in excellent condition, no issues. This is 1 of 3 X20u's I've owned. I preferred it to my SOtM sDP-1000 and Ayre QB9 DSD (both of which cost considerably more). Note this DAC has Ric Schultz Level 1 AC mods, which bypasses the AC filter and front panel switch circuits and wires the transformers directly to the circuit boards. This means that the power switch does not function (power on/off by simply unplugging, or simply leave on since draws minimal current at idle). The effect of this simple upgrade is quite significant. So much so it persuaded me to purchase another X20u which Ric Schultz modified to full Level 2 standards (hence the reason for selling this one).