Xandria is worth looking into, they're very symphonic. Delain is a bit on the pop side of things vs. the symphonic side, but still good. You said you're a fan of Within Temptation, so I'd definitely recommend Delain. Leaves Eyes has the problem where they can be a bit growly in some of their songs, but others are quite lovely.
Krypteria and Sirenia are two other names that might be worth you looking into. They're a bit on the gothic side of symphonic metal.
Actually, I've found that the best way to find new bands is to just make a Pandora station seeded with the artists you like. It's how I discovered most of the metal bands I like, actually.
This is amazing! It combined two things I love, and it's performed so well.
Can you give more information about this? I cannot find anything about it on the website of Epica or most of the usual places where I look for music.
I would love to buy these songs digitally. I found their music CD on Amazon here, but do you know a place where I can buy this digitally to support Epica?
If you like current Arch Enemy (their latest album), the first 3 albums of The Agonist (everything before 2014) have the same singer.
Can't say I listen to Jinjer or Cellar Darling, but I listened to those two songs vs Arch Enemy and I'd say they're all pretty different. Cellar Darling is pretty good it seems, not really a Jinjer fan (those male vocals/growling kill it for me).
I'm quite picky about my music though and it's all over the place genre-wise. I'm partial to clean-ish vocals(or a mix) with no male growling/screaming, The Agonist being one of my few exceptions.
I would see about digging through the first 18 or so pages of this subreddit (last 2 1/2 years or so), plenty of good stuff here.
You can also try http://everynoise.com and search up artists on the top right. Then click on a sub-genre and click around for samples of each band. It's not perfect, some bands may not sound exactly like the samples because of a poor sample song choice, but it's pretty great to quickly search around for new bands to listen to. Word of warning, turn your audio down a lot before clicking a sample they're seemingly quite loud.
With that said, a few I would recommend that you may not find here: Amaranthe, Unsun, ReVamp, Krypteria