I like the ZS, and it has been serving me well. It is a very capable performer up to its price point. However, I wouldn't go as far as to claim it as the best under $1k. There are several candidates reported to be equally capable performers in that price range, in addition to the DMP A6:
0. Wiim Pro / Pro+ ($180/$220)
1. Volumio Primo V1 ($400) stream/DAC w/ the perpetual subscription of Volumio;
2. Matrix i4 mini ($650)
3. Volumio Primo V2 ($750?) stream/DAC
4. Mercury V2 ($850)
5. Volumio Rivo ($1,050) streamer
I believe that over time, the lower-priced market will become saturated with these affordable yet capable performers. Their functionality will likely be enriched to include several useful and desirable features such as PEQ, upsampling, and possibly DSP. Hang onto our good friend ZS until those promising days arrive.