I believe the 103 likes a heavier arm, at least medium mass...?
If you run the DL103's factory specs (e.g., dynamic compliance of 5) for arm/cartridge resonance, you'd need a tonearm with an effective mass of 30g or so. Apparently this is not the case and Denon's compliance spec may have been derived from a different methodology than others. Although I have no direct experience with the DL103 series, I have an audiobuddy who has used one quite successfully on tonearms with an effective mass of 12g. This forum also has plenty of confirmations that the DL103 series works very well with medium-mass tonearms.
12g is a very mainstream effective tonearm mass, shared by the Rega RB30x series and even the tonearm on the Technics SL12x0 series.