I have used a Benchmark DAC1 and a Lavry Black DA10 direct to a pair of Meitner MTR-101+ monoblocks via 1-metre single-ended interconnects (Canare StarQuad, Mogami 2534, DH Labs SilverSonic, Cardas Golden Cross)--XLR-to-RCA in the case of the Lavry, as it only has XLR outputs.
I found I preferred running the DACs first into the Meitner PA-6i+ preamp. Direct-to-amp is slightly more "pristine and delicate", but, for my ear, loses too much in dynamism and bass "slam" and articulation.
The input impedance on the MTR-101s is 22 kOhm and the output impedance of the Benchmark is 30 ohms, but I don't know the output impedance of the Lavry.
In any case, the foregoing was just an experiment, as I use three sources (FM, turntable, CD) and require, if nothing else, the source selection of a preamplifier.
I have tried some upscale passive preamps, too, but found I prefer a quality active preamp to passive/TVC.
Hope this helps.
Regards,
Joel.