Drop-D tuning is almost fine with any pickup specially the ones you mentioned above.
I can personally say that the D-Activator is an awesome pickup since I have it installed in one of my guitars.
The D-activator is supposed to mimic an active pickup minus the usual sterile sound and w/o the need to use a battery.
It has clarity, heaviness, dynamics and warmth that most active pickups dont have.
However, if you want to get really down "LOW"... I mean Drop C or B all the way.
Most people prefer an active pickup for that application since it has more clarity than a passive pickup and doesn't get easily muddy on the low-end.
Check the Duncan Invader set or the good old EMG 81/85 combo.
Just an added info for Drop B or C tuning.
You will need to use heavier gauge string. You need to experiment on this one so you will find whatever works for you, start from the lightest possible for Drop-C .012 - .052 and move up to heavier gauge to prevent serious string buzz, reduce string floppiness / looseness, proper string tension, and for the added heaviness when playing riffs.
You'll need to do some serious intonation for your guitar, the open strings will be in tune but as you go higher the neck, you'll notice that the strings gets out of tune.
For best result, I think you'll need a "Baritone guitar" from which they usually have 26.5" to 27" scale length as opposed to the normal guitar scale length of 25.5" to do this job properly.
