The Andromeda has recessed vocals though. The Andromeda S version has more forward mids, but I wouldn't even compare it to the hd6xx because the treble is also very bright (not in a bad way) and the hd6xx had somewhat rolled off treble.
I want very natural/organic sounding female and male vocals.. maybe even bordering on what treble lovers would call a dark presentation..
Hm...I never found the Andromeda vocals recessed. At least compared to some very V-shaped earphones. It definitely has a strong treble though which I like and find it a plus over the 6XX (I own one). Organic is a good way to describe the 6XX. Tbh, I think the open back aspect plays a huge aspect over earphones. It has nice vocals and a spacious feel to it.
Roxanne is one of my favourite earphones and definitely has some great male vocals and sounds great with rock but the female vocals and compatibility with other genres like pop is definitely lacking.
Actually, I would look into the Empire Ears ESR as well. It has great vocals like the 6XX but has a very effortless and natural feel to it like the 6XX. Maybe a tad bright also though.
Also, the JH Angie (some of the best vocals ever).