I've learned a few things in my time, so here's a few pointers;
I don't think there is really one brand of bass that is dominant in extreme metal. It seems like a lot of the Florida and New York death metal bassists used these random spiky basses of which I have no idea of the brands. Schecters are pretty solid (not a fan of the stock EMG HZs though), you can't go wrong with Ibanezes, or you could go for flash and get a BC Rich. Go above the first-level price range though, their entry-level electronics kinda blow. Or just go all out and get a Warwick. Warwicks are amazing and can give you any tone under the sun.
If you're playing with a pick don't use actives, it sounds too harsh and will cause clipping really easily. I'm pretty sure that contributed to frying my SVT350H. If you're using fingers anything goes, but I prefer the sound of two jazz pickups split evenly because it's really fat and clear and has a nice high and mid range.
Mids are your friend, they give you presence. Use them to give yourself a full tone. A lot of bassists think that it's just low end for the boom and high end for the clacking, but that's stupid. Maybe in other genres of music it may work, but in metal, particularly death metal, where the low end is the focus, you need mids. Same goes for guitars, turn up the mids on your guitarists' amps when they aren't looking.
24 frets are nice if you do a lot of tapping (I do), but otherwise it probably won't make a difference if you don't.
Using a little bit of overdrive and chorus can boost your tone and tone and give it a ton of definition. I learned this from a band that is generally disliked here but they start with a T and end with an L and rhyme with school.
Don't let guitarists tell you how to play your instrument, and if they do, just backhand them. They'll probably start crying and leave you alone.
There's my two cents, hopefully something in there helps.