these impressions match mines about cable 198. huge bass, good for bassheads or for those who seek for a warmer tilt in their combos. this increases the chance of both cables using same wire. although there is a large difference in the quality of their plugs (besides of price).
always i see a wire of 4 cores * 63 strands copper, dunno it will be like cable 125 wire, or like cable 065 (jcally) wire. cable 125 is supposed single crystal / high purity occ copper, and cable 065 is supposed 5n ofc, and there is a night and day difference.
ISN C4 is advertised as single crystal copper; i don't own it, but guess it could be very similar to 125. i haven't got DM6 either, but based on impressions and measurements of DM6, i think 125 / ISN C4 would be a good copper election, in the $60 range. black background and great bass.
a bit more expensive ($75 range) would be cable 170 (cema electro acousti up-occ copper litz), bigger soundstage and better plugs. a bit tighter bass, but i think DM6 is also well served of bass. highs are a bit tamed but not swallowed, they keep good detail. higher resistance, but not much difference considering your DAP has got 1ohm output impedance.
and a bit more expensive ($85 range), cable 210 (nicehck oalloy up-occ copper & silver alloy, litz), same soundstage than 170, worse plugs and even higher resistance, but i love the bass with this cable, and the silver component keeps airy and detailed, while smooth, treble.
anyway, tonal perception differences between cables are subtle. you can obtain more tonal variation by rolling tips (try foams to tame 8-12kHz peaks), by foam/tape mods, or by equalizing, way cheaper. this is why i agree with
@battosai. i'd prioritize quality of wire (soundstage, black background), and then tonal perception influence, so a hybrid cable (copper and silver wire) could serve as well as copper for your DM6 (same for T800).