I may be really off, but I saw that no one was responding, and I don't want to leave ya hangin.
First off did you know that Brian may has signature model pickups (I'm not sure who makes them....and I sure hope they're not the kent armstrong ones you speak of)
I'm not sure if the pickups you speak of are humbuckers or singles, so here are my suggestions
Brian may uses single coils from what I have seen.
Perhaps a Dimarzio Humbucker from Hell would do your job well (it is a dual coil full-size that has the brilliance and clarity of a single)
The Dimarzio Tone Zone does a good job of both of your sounds desired(As far as I've seen)
For single coils try a Dimarzio(Ok -I'm biased a little) HS-3, or Pro-track. The first being the lighter sounding, and the later more of a screamer.
I think to get the sounds you are looking after, some switching may be required, either to different pickups or series/parallel in the same unit.
Tell me your pickup configuration (H-S-S S-S-S H-S-H etc.)
and your switching controls and I'll give you my best suggestion.
In the meantime checkout www.Dimarzio.com They have sound clips for certain models...that might help
Oh yeah I think Seymour makes Brian's pickups I think they are called the tri-sonics and they are on his Guild signature models.