Well, I'm a little late to the game but I picked up a nicely used W4S DAC-2. I chose this DAC based on the reviews and all the write-ups from Polk members. Also, I decided not to purchase an entry level DAC ($200-400) hoping for a significant improvement over my Sonos player. I could not be more happy with the purchase. It was very easy to do A/B comparisons against the Sonos via input selection with level adjustment. Immediately, I could identify the DAC-2 being very detailed and dynamic over the Sonos. The bass is very tight and fast. The highs and mids are smooth, cleaner with more detail. I would say this DAC just sounded more musical and this was noticed with every song that I've played so far. I use to enjoy the quality coming from the Sonos. But after listening to this DAC for an extended period and then returning to the Sonos alone, I could not live without this DAC in my set-up. It will be around for a long time. This is my first external dedicated DAC so I have not compared it to anything else but I would say that this has been one of the best improvements (so far) that I've made to my system in terms of SQ.