I don't know if this helps...but the JH13 has excellent synergy with the DX100....the best I've ever heard them sound, and that's saying a lot.
I use mid level gain for my JH13's, but low gain would be normal to use as well with IEM's. Select the gain that gives you the volume, volume adjustability, and level of hiss you prefer. Proper gain matching to eliminate hiss is less of an issue with the DX100 as it appears to be hiss free at all gain levels with all headphones I have tried.
Thanks, I haven't tried the JH13s yet - I'll give them a go too.
I haven't heard any hissing through the JH16s at Mid gain - High it too loud