OK, so here's where we are at the moment:
Emerald - Could certainly do what I'm after and I love the clips.
Mules - An eternal favourite so no real surprise, though I was concerned it would be a little too vintage to replace an HFS.
Riff Raff - Seems popular and I confess it's not one I'd considered as again, I didn't think it would have the balls to replace an HFS.
VHII - I hear great things about the neck pickup but had never thought about it for the bridge.
Abraxas - Surprisingly, no support for this one and I thought it might have been a good idea.
Holydiver - I had thought of this one as well but dismissed it as I already have one in my Jackson. I suppose I could always find something different for the Jackson and transfer the Holydiver into the PRS.
I no nothing about the technical side of this so I'm probably very wrong but my feeling at the moment is that Mules, Riff Raffs and possibly VHIIs won't be hot enough to replace an HFS. The Emerald still appeals to me and I'm not ready just yet to totally discount the Abraxas. I've also been looking at the Black Dog and certain aspects like 'deep bottom-end, muscular mids, smooth highs and more output than a vintage PAF' appeal to me, as does 'designed for players that need a vintage voiced pickup with extra weight in the mid range'. However, the description of 'An aggressive, throaty humbucker' makes me think of the Nailbomb and I obviously had a bad experience with that. Of the contemporary humbuckers, I already like the Holydiver and I'm not averse to the idea of swapping it out of the Jackson and trying something else in there but I'm unsure if any other pickup in that range would do what I want. The Crawler may be a possibility but I've always associated that more with Strat-style guitars rather than mahogany.
It doesn't seem like I'm much further forward does it, lol.