#1
Ive decided i wont swap the pickups in my Jackson, instead im gonna swap the pickups in my Epi Explorer coz the EMG HZ's are now startin to sound dull to me

but, now i dont know which pickups to choose, Seymour Duncan JB/Jazz combo, SD Distortions or mabye SD Invaders (but i dont know if there passives or actives)

which would be better? there all roughly same price

for those that want to know what music i play, i play lamb of god, children of bodom, disturbed, dethklok, sevendust, stuff like that so i want a nice heavy sound

for those who will say "get a new amp", i am getting a new amp soon
Gear
Epi Goth Explorer
Schecter Demon 7
Jackson JS30 Rhodes (modded)
Line 6 POD HD500
Roland Cube 60
#2
I just did a pickup swap myself, and I was actually looking at pretty much the same things. The JB's are the best of the bunch for versatility, and the GC rep and I actually thought the Distortions sounded heavier than the Invaders. It's all up to you, though. Check out the sound samples on SD's website if you haven't already.
#3
Lamb of God use (or at least have used) a SD Custom/59 combo. That, imo, is way better than JB/Jazz.

Another thing to note, is that Dethklok just use stock Gibson pickups, so that alone should tell you that it's really not about getting a heavy pickup, it's about your amp.

If you're getting a high gain amp for metal, I'd actually stay far away from Distortions, Invaders and anything similar. Pairing high output pickups with a high output amp generally does not yield very good results. Just too much gain there fighting with each other, and you'll most likely end up with a mess.

I would recommend getting moderate output pickups, like the combo I suggested.
Spin 'round carousel when your horse isn't screwed in.

My band:
Fractured Instinct
(For fans of Death/Groove/Prog Metal)

Ibanez RGA42E
Ibanez S420
LTD H-301
Ibanez RG520
Peavey Predator USA
Douglas Grendel 725
Line 6 Pod HD500X