Several folks I know and myself drive ATC SCM50ASL(T) speakers directly with the Weiss DAC501. Most find the many DSP features useful. As far as I know, none of us are planning any further upgrades. One auditioned the T&A 200 and preferred the Weiss. Most folks out there that have made the comparison with Dave, prefer the Weiss.
If you are considering something as expensive as the Bartok Apex, also audition the new Weiss Helios which is in the same price range.