I compared the QB-9 DSD to the Codex and kept the QB-9. The older DAC sounded more refined and articulate. I feel it would be a worthy upgrade and these days you can find them on the used market at very reasonable prices.
Having said that, I've since sold the QB-9 and use a Benchmark DAC3 as my primary source.
Having said that, I've since sold the QB-9 and use a Benchmark DAC3 as my primary source.