The PD7 is probably the best pedal you can get for metal at that price range, but the Digitech Bass Driver's worth a look as well, very versatile as it models a bunch of different pedals.
EDIT: I'd like to add that I play in a metal band too, and I find that the band's overall sound tends to be a lot clearer and generally better when I DON'T distort my bass - it ends up sounding muddy sometimes, especially in rooms that aren't too good!