Hey green bro!
Nice that you made your own topic (looking at all the vids, yes, it's good that you made your own one, hahaha!). Before I listen to every single song though (there are a lot, lol) I thought I'd post a few (so you don't wait forever) and I'll comment on the three songs that I listened from the list so far.
The first one, um... Scar something (dammit, I had it in my mind, lol) was quite good! And interesting. It had that 80's feel, thrown into this neo world, with some "death" undertones. It's quite interesting seeing how it all worked together, and yes, that guy has a great vocal range (good that he can sing too, not just "grunt" ha ha).
Second vid I saw was the one by... crap, lol Efiserum Eff...something, lol, the melodic/symphonic/death/folk metal one. It's something similar in a way as to what I'd listen to, except slightly distinct. I was digging it actually, and it's something typical of some of the more (cheesier? lol) power metal bands, that sing about legends and dragons and what not, which is pretty cool in my book.
Third song i listened to was the first Epica one you listed. I think my friend will dig this! She got me into Nightwish (symphonic metal FTW!) and this band somewhat reminds me of them, which is a big thumbs up! I don't mind the grunting in the background either, infact it reminds me of some Evanescence songs (Amy Lee is a brilliant singer!). So yeah, you've opened me up to a few new bands so far, which I will look into further (I gotta listen to your other links too, lol).
In the mean time, I'll post a few songs I find interesting.
All right, thought I'd post a couple more Helloween songs (seeing as they're the fathers of Power Metal). Funny you say, my friend is into grindcore. I've listened to Pig Destroyer and think how the drummer doesn't get tired, lol. I don't listen to much Thrash metal, for similar reasons you give, although I have to say I dun mind a few (Metallica in this case doesn't count, lol, they're so versatile that you can't just call them "thrash metal" and they're a band I'm liking more every day). And Mike, I agree, it's why I seek the more melodic stuff, coz I can't listen to RARARARARARA or something with awful vocals and really plain and boring instrumentals. Anyways! lol....
This is classic 80's symphonic power metal!
This song is probably Helloween's only Thrash metal song, but it's complimented with typical Helloween vocals and power metal chords! I'm loving this song more every time!
Now for a band that was inspired by Helloween (I'm pretty sure). Stratovarius: technically Neo-classical power metal (or speed metal), the vocals are inspired by 80's power metal, meanwhile the instrumentals are inspired by classical music, would you believe?
This song got me interested in them!
This one is an instrumental. I swear, if Bach and Beethoven and Mozart and the gang were alive today, they'd be metal gods!

Finally, a song by one of my favourite bands, Queen! Sure, Queen are rock and pop and many other genres, but not metal. Although, one of their songs (made in 1975 I think?) may very well be the very first thrash metal song (by accident even? lol). Some people say it has influences, but it would have been very progressive at the time wouldn't you think? It's no wonder Metallica covered this song!
Well that's all from me for now, enjoy while I listen to some more songs, ha ha.
EDIT: You put Powerslave by Iron Maiden! Woot! I got that album not long ago, loving it!