Firstly, what do you not like about your current pickups? If you have no idea, just keep them, you'll do fine with it. Pickups are only part of the equation, there's still the pedals and amp to get the sound you want too.
to get the sound u want.. just buy a hell load of pedals. haha... like buy two od's buy a delay. buy a metal muff or something... always works. just get enough pedals until the real tone of your guitar is lost. yeah.
Grunge and Fender 25r can't give you enough gain for your thrash, death stuffs yeah i presume? If you really are satisfied with your guitar, amp, effects and feel that it isn't giving you what you want, the need for a pickup change might suffice. Otherwise do not change your pickups la, do work on the rest of your rig first eg. another gain pedal to boost your grunge or an amp with better distortion and stuffs.
Yea man..........instead of changing those pickups get another gd gain pedal 2 supplement ur current setup. Examples wld be BOSS DS-1 or MI Audio Crunchbox. Depends on ur budget too. Either way, another gain pedal wld be cheaper than new pickups.
Death/trash metal use Boss DS-1 or Crunchbox???
Dude.. That can only bring you to AC/DC at MOST..
My suggestion?
EHX Metal Muff (with Top Boost for versatility)
Beez modded Boss MT-2
Line 6 Uber Metal (I don't fancy this but it gets the job done)
Rocktron Metal Planet
Guyatone MM-X Metal Monster
Digitech Death Metal
Landmine
I'm personally enjoying the EHX.. Before that was caught up in deciding btw that and the Beez modded MT-2..
A pickup swap is not really recommended unless you really aren't please at all with the original sound..
if intense drive is your thing (& nothing else), it's worth investing in active pickups. however, a good amp can adapt to different drive needs with guitar pickups not being the primary contributor to intensity.