DAC suggestions for a reasonably modest system

I have two systems currently fed by a SMSL SU-9n via Y splitter.  It's time to add a new/used DAC and get rid of the Y splitter.  New DAC will feed a VTL TL-2.5 + VTL Stereo 90 or a couple of different vintage SS amps (Sony TAN-8250 or Luxman 5M21), and just for fun, maybe a couple of Dyna Mk VI, running Magnepan 3.6R.  The SMSL does a great job overall, but seems to be a better fit with the ARC SP3a1 + SET or SEP amp into Altecs.  For those of you that have had the SMSL or similar level DACs in a similar system to mine and have moved up the chain, what gave you a nice step change?  The Maggies, however imperfect, are delightfully revealing and prior DAC changes were definitely more apparent with them.  Budget is $1000-1500, and I have no issue with buying used good quality stuff.  None of my system is less than 20 years old except the DACs.