We are the North American distributors for Rockna so I thought I would jump in on this conversation. To be 100% honest we have A/B tested most of the dacs mentioned in this forum and they are all very good dacs. I believe it comes down to personal preference. I do however like the i2S connection better than any other connection because it eliminates some parts and gets you closer to a direct connection to the dac chip. The main reason we took on Rockna was because their dacs and server competed against much more expensive dacs and servers sound wise and build quality is also excellent. The other stand out dacs that we like are the Mola Mola dac and the Total dac. Mola Mola is another well built great sounding dac at a reasonable price.
We feel that it is difficult to say you have the best in regard to dacs but Rockna is definitely up there with the best dacs in the world.