I have been looking for an IEM mainly for metal as well with very similar factors to you.    So far I'm leaning towards the CK-10 even though there are so many different opinions on the bass. Haven't heard of them with my own ears yet but I'm looking for the best IEMs that follow the factors above for around 250 AUD. AUD/USD both are about the same now, so hopefully it doesn't make a difference, but MAN the prices are high in Australia. $380 AUD for the CK-10!  Anyway...