I have an SL3 so I could offer an opinion for what it's worth as I#ve tried a few pickups in it. Other than mine being made in Japan, I think it's essentially the same as yours. For your information, I also have a Miracle Man in the bridge of mine but I've also had a Holydiver and A-Bomb in there too. In the neck and middle positions I've been using Trilogy Suites but I've just sold them. If you search, you'll find reviews I've written for all of these pickups but here's a brief synopsis:
Holydiver - A lot like the Miracle Man in my Jackson but not quite as tight and not quite as aggressive. It's smooth and very 80's Metal but with an overdrive it can go further. I have it in a PRS now and that guitar takes me up to 80's Metal and then I use the Jackson for anything beyond that.
A-Bomb - VERY aggressive sounding, very tight, edgy and hairy. IT has a very 90's Metal feel about it. Nothing like either the Miracle Man or Holydiver. I always thought it needed a big slab of mahogany to tame it so didn't really suit the Jackson so I sent it back.
Trilogy Suites - Great single coils that will shred all day long and are surprisingly versatile. I sold mine because I'm not a big fan of single coils and there was a bit of a volume drop when switching from the Miracle Man. I'm replacing them with bridge versions of the Sinner with baseplates fitted. Tim tells me they'll be very fat, fluid, precise and like humbuckers but they haven't arrived yet.
The other one that has always appealed to me is the Warpig. There's been a few people with Jacksons who have had great success with a Warpig so that could be an option. I imagine the Black HAwk would also work well given your low tunings.
If you keep the Miracle Man in the SL1, try either Trilogy Suites or Sinners to go with it, depending on if you like single coil tone or something more humbucker-like. If you do that, I think I'd be tempted to try either a C-Pig or Black Hawk in the SL2 but I'm unsure what would be best for the neck.
Do it the other way around and put the Miracle Man in the SL2 and I'd try a Cold Sweat in the neck to go with it. In the SL1, I'd probably try a C-Pig with Sinners or a Black Hawk with Trilogy Suites.