as with subversion, im a seymour duncan supprter as well. to me duncan gives a more organic/classic tone. whereas dimarzio gives u a more mordern and very specific sounding tones.
What wood is the body of your guitar made of?
because in certain types of wood, the Screaming demon serves as an awesome bridge pickup with lots of bite and and clarity as well. its a little on the bright side, so gotta becareful what you put it in.
as for other duncans for heavy rock and metal, the PATB-2, DD bridge, Custom, Custom 5 would serve your needs well. depending on what kinda tone u want.
Custom (ceramic mag), its like a beefed up version of a PAF type pup with lots of bite and a pretty focused low end.
Custom 5 (A5 mag) would give u slightly scooped mids while maintaining clarity under high gain with very focused low ends and highs that wouldn't be too ice-picky.
PATB-2 and DD has ceramic mags as well (but the DD has an oversized one).
the PATB-2 is one of the duncan's best kept secrets, by looking at just the DC resis you would think its a crazy insanely high output pup. but with floating bridges, the PATB-2 works wonders by having a nice fatter tone to make up for the bridge causing the thiness of the tone.
DD would be a very aggressive pup and wont do cleans very well, but if you're looking to make the guitar a full time metal/hard rock guitar with lots of gain used, it could be what you need.
Noe that these are just bridge pups, theres alot more i can write about neck pups as well, but it would just go on and on and be too long for a post.
I can do some descriptions of some of dimarzio pups as well. PM me if u want the details, i dont wanna flood the forum with reviews
Cheers,
Ken