I have the same guitar, tuned to drop f#, and I tossed a Dimarzio D-Sonic in the bridge. Made it sound heavy as hell while still letting me jump from sludge doom to prog metal. Still haven't decided on a neck pickup, but I may try a Liquifire to see how well it matches.
Definitely agree that the stock pups suck. Way too muddy for my tastes, and it was nigh impossible to get a good tone at f#.