first i want to know what kinda amp u're using...
for powermetal, most hi-gain amps have the distortion..
but sometimes it may be a bit to crunchy, or just not sounding right.. for the first.. check your EQ.. i would recommend much treble(7-10), little mid(2-4), and some bass(6-8), but theese setting sound good for me.. but maybe not for you.. i got a marshall JCM 2553 head...
Still.. u can produce a tone u want with many pedals.. try some Boss-stomp boxes(metal Zone, Hyper-Metal etc).. or maybe buy an preamp instead.. like a used ADA Mp-II.. i really don't like stompboxes that much.. or u can buy a multi-fx pedal/unit.. then u'll probably can make the sound u're after..

But, the most important thing.. TRY THE BOXES/FX ON YOUR OWN AMP! some fx sounds great on some amps.. but they sound different on others..

if u got money.. get an overdrive/dist box with a tube.. it's another dimension..

BTW, i have some friends who thinks hybrid amps are better for powermetal.. like Valvestate.. i don't think so.. but it's all about opinions.. u have to find the sound u like.. not others..