Official Sonic the Hedgehog Fanatic
Film/Music Snob Extraordinaire
I'm gonna guess that K-OS song came out around the late 90's or early 00's, because hearing that instantly brought back memories of hearing it a lot when I was a kid.
Home is where the needle marks
Try to heal my broken heart
Anthrax was on Megaforce (Sony) and then Island (Atlantic) in 1985.
Slayer was on Def Jam (Universal) in 1986.
Metallica started on Megaforce (Sony) then to Elektra in 1986 (Warner).
Megadeth was on Capital (EMI) by 1986.
So there's big 4 thrash because there was big 4 record labels. They were all American bands that were given the proper promotion and distribution during a golden era.
Coroner and Kreator were on Noise, an independent German label. Destruction and Sodom were on Steamhammer, another indy German label. Basically big 4 is just an awareness thing created by the industry at the time.
More metal in Rock Band:
Sounds like the better thrash metal bands were on German Indie Labels. Not that it's much of a surprise for the elite bands of a metal sub-genre to be on Indie Metal Labels. Do Agree with the "Big Four" being a marketing construct for Thrash considering that there were many other US Thrash Metal bands still getting the shaft as far as record labels/marketing/media hype during Thrash Metal's hey day was concerned.
Bands I'd love to see as DLC for Rock Band:
Bal Sagoth 
UO: "The Perfect Kiss">Joy Division's entire discography