Heavy metal? That was one of the biggest sore spots on the OII MKI (aka SR-007A) when I owned it, and from what I briefly heard with the Ether when I had one in-house for a weekend recently (although it was under-amped, admittedly), I wouldn't say it works well with that kind of music either. Both the OII MKI and Ether are relatively neutral headphones, and in my experience, neutral headphones just flat-out don't work well for metal in general. Sonic coloration is a good thing for metal, IMO.
I also recommend a huge upgrade on both your DAC and amp if you intend on getting any >$1K headphones. Well not that what you have now is bad, but both the OII MKI and Ether are going to be super-revealing of your DAC & amp.
And you need at minimum something like a KGSS to get anywhere close to decent performance out of the OII MKI, but a Blue Hawaii would be better. If you don't want to hunt down a KGBH or wait for a BHSE, it'd likely be a lot easier and more cost-effective to just go with the Ether (obvious gear to pair with that would be almost any of the upper-end Schiit stuff, among other options too of course).
Btw, where do you live anyway? There are meets in Canada semi-regularly, just hit the Meets forum.