I'd definitely recommend BKP. Both of the guitars that I use for Metal have them in and they sound INCREDIBLE. I have a Jackson which I use for Death Metal which has an Aftermath, which sounds very defined and generally brilliant, so I can recommend that. Aftermaths should work very well considering they're geared towards lower turnings. You can also get bolt-less black covers if you wanted to keep the active soapbar look.
However, if you wanted to go BKP, I'd recommend emailing them with your guitar specs and a description of what you play. The owner, Tim, will usually respond with a suggestion. He knows his stuff!
I've not had much experience with actives, but if you think that the Blackouts are too dark, then maybe EMGs would be in order if you wanted to stay active? I believe they're slightly brighter than Blackouts; but someone with more knowledge should chip in and correct me here.
It all comes down to personal taste. I like the organic nature of passives, but actives still sound very cool. There's a reason that so many Metal players use them!
On a side note, I don't think I've ever heard Death Metal on an 8 string. It must sound huge
