The only humbuckers I have tried in a PRS are Rebel Yells in a Standard 22. I really like them. In that guitar they are fat with a lot of output and a real attacking upper-mid. Not tons of low end. A really fun pickup to play with.
There might be other pickups that do the tone you're looking for better. I don't know. But I can confirm Rebel Yells sound great in a PRS, and sound great for Eb/drop Db tunings. They have the prominent harmonics to pull off Zakk type stuff, even if they are nothing like the pickups he uses in other ways, and they are fat and high-output enough to manage Satriani and Alter Bridge stuff.
I knew someone with Crawlers in a PRS Custom 24, and he was really happy with them. I never heard his guitar plugged in, but as far as I know they could also be an option. Thicker sounding and a bit darker, from what I've heard.