Technically, the Six has one more DAC for each channel. Three, where the Dual has two ladder DAC's per channel. Another improvement in the Six is an improved output stage. This is all on the website, and the Six is now the best one chassis DAC from Totaldac. Sonically, although never comparing these two DAC's, it should be about more of everything you like about the D1 Dual. More transparency, lower noise floor, more dynamics, more dimension, etc. I had the Monobloc DAC's before, and they were better than the D1 Dual, but the Six is likely very good, and is safe to assume the reason Vincent dropped the Monobloc, as I do not see it listed as an option to buy anymore, so I think the Six should be very good!