That Prokofiev thing sounds interesting, I've been wanting more of that in music ever since I heard Blood Axis' 'Reign I Forever', which samples Romeo and Juliet.
As for Grave Digger, yes. That said, 'Heart of Darkness' and 'Knights of the Cross' come well recommended. Grave Digger are my second favourite of the big 80's German 'real' power metal bands, behind Running Wild. If you haven't heard Running Wild, by the way, then you are seriously behind. Get the Branded and Exiled/Under Jolly Roger/Port Royal trilogy NOW!