so i installed 2 subs and amp into my sc300. It sounds nice and all, but the humming sound is sort of annoying now...It is the ground that's making the humming noise?

 

Sounds like a ground loop. You should probably run a thicker wire for the ground on the amplifier or move it to another location see if that helps. Also, you may want to add a 10-gauge wire from the battery's negative post to the chassis.