You should definitely look more into Nine Inch Nails in particular. The actual band is all just the lead singer. He writes, arranges, and performs all the music on his albums. He also composes music for movies. Actually, the song I chose is one of my favorites from them, because it goes from very hard thrash metal almost to a melodic piano piece with vocals, then back to metal.
Slayer is more or less play the most brain melting crazy heavy metal solos as possible. Extremely high level guitar playing, but it's not for everyone. I'll be the first to admit.
Necrophagist is kind of similar to Slayer, but maybe a bit more technical guitar and polished sound. The only other difference is the vocal delivery.
Embedding changed. I'm not sure why, but all the sudden you had to delete that part. Ya, it's kind of annoying.