I'm using iFi Zen Streamer USB to Wyred4Sound DAC2v2SE. The iFi Zen was a little kludgey for initial setup but it sounds far better than I expected. At a $399 price point I wasn't expecting much and I'm still pleasantly surprised.
The Zen stream was an interim purchase for me as my previous streamer had died and I needed something quick. I assumed I'd be trading up within a few months of finding my next streamer.
Maybe not though. I'm still really enjoying the heck out of the iFi zen. And I've got a Matrix Audio X-SPDIF 2 on the way to serve as an I2S converter between the USB iFi Zen and the I2S interface on the DAC.