I was in the same boat with the D2, but the DX50 is much, much, much better for heavy metal. It really renders drums and rhythm guitars really well, even through my B2's (which are analytical, super-fast, airy IEM's and I assumed they were to blame for metal never sounding quite right out of my D2/Zo/B2 pairing). Swapping the D2 for the DX50 made a world of difference, everything is super punchy, spacious and clear.
The tradeoff for me seems to be that the D2 rendered female vocals much better. I feel somewhat detached from stuff like Celine Dion on the DX50. I chalk that up to not having a band between 1khz and 4khz on the EQ (D2 has a 2.4khz band, which IMO is much more useful than the 4khz band)