Marco doesn't sing on "Meadows", does he?
Those male voices on that song are gospel singers, if I'm not mistaken.
Re: Marco's voice...it took a long time for me to get into as well. Then again, I've been a Nightwish fan since before Marco joined the band, so I remember when his voice was still "new". It really runs hot and cold with me. Some days, his voice is f*ckin' killer, and other days, it annoys the hell out of me.
One thing I have said before, Tuomas as a songwriter, really knows how to bring out the potential of any singer he has. Marco has improved vocally with every album (I know he's been singing with Tarot for ages beforehand, but I have never heard their music so I can't make a comparison to anything other than Marco's voice from Century Child to now). Nowadays I have more moments where he sounds great to me, than when he annoys me. Especially after listening to the radio edit of "The Islander", which I've said more than once on this forum that it's my least favorite song of the album. Even seeing it live did not change my mind on it. But when listening to the edit of the song, and the part where Marco's vocals are dueting with Anette's (towards the end, the "this is the long forgotten..." part). I don't know why those vocals were not kept on the regular version, but he sounds absolutely great on it.
Another fantastic example, for me, is "While Your Lips Are Still Red". I would have to say that right now, it's one of my favorite Nightwish songs. My opinion about Marco's voice definitely shifted more towards a positive attitude (although I never outwardly disliked his voice). I do agree that he should sing more in this style, but his angrier voice certainly gets the job done for those songs like "Bye Bye Beautiful", "Slaying the Dreamer", "Master Passion Greed", etc.
Anyway, I'm rambling on at this point so I should probably stop.