Blind Guardian has done some great power metal with heavy symphonic representation recently.
Here're five from their last two albums which are particularly interesting (though the two from the
album At the Edge of Time are really the only two on that album that are as symphonic, while pretty much all of Beyond the Red Mirror, including the song "At the Edge of Time" are very symphonic.)
There's also some pretty good extreme metal with symphonic elements, but the arrangements aren't always quite as complex, since it's mostly one or two band members laying down the best of what they could, and I'm pretty sure that they don't quite have the experience of professional conductors, so might be better called metal with symphonic elements/instrumentation since some of it, like; Mondstille apparently don't have a whole symphony backing it. However, of these, I think Carach Angren sounds pretty large in their sound, enough to fool a person into thinking a dozen or maybe more were behind this when it was really one or two people doing all the orchestral-like stuff. I could also see it being seen as kinda cheesy, but I think it's worth giving it a brief try.
Then of course there's the "synth-phonic" (
) album Time I by Wintersun, which has all computer-generated orchestrations for those parts, so the tones/timbres of them may not be so enjoyable to some, but it's quite complex and may be enjoyable to some here, (I know I enjoy it quite a lot, though I've seen quite a lot of vitriol thrown its way from people on Metal-Archives.)