Came on this thread (obviously) late but thought I'd chime in... I called W4S right when the Dac2 came out with the same question... Spoke to one of their techs and he shared that as long as it was (obviously) a digital signal, There should be NO difference, it's why they designed it... Shares common components and design.
W4S DAC1 & STP-SE vs. W4S DAC2 as digital frontend
With Emerald Physics CS-2.3's (standard Behringer processor) fed by W4S ST-1000 & ST-500, and using as sources a Marantz CD 5004 (for transport only) and 2010 Mach 2 MacMini music server running Pure Music software, is there likely to be a significant difference in, e.g., resolution of detail, transparency, dimensionality, etc. between a front end consisting of (i) the STP-SE and the new DAC1 w/asynch 24/96 USB and upgraded caps vs. (ii) the DAC2 alone? In this setup, will the stand-alone preamp really let the amps sing noticeably more than they would without the preamp?