the best place i like to start is with the guitar because that is literally where all the magic starts.
my rig is simple for metal:
preferred guitar
preferred effects
some sort of EQ (i use a boss 7 band pedal)
then an amp that has the tone you want OR since i'm unwilling to spend a ton of money on the head i actually want (mesa triple rec) a raven rg100h will do because it has a super clear clean channel
the quest for tone is endless.
i'm having a 2x12 birch dovetail cab made up soon with some eminence swamp thang speakers loaded in it. you have to get what you want, copy som of your favorite artists and experiment. dont be afraid to use the hell out of guitar center's 30day satisfaction guarantee :)