ok so i want a new amp my budget will be around $600 aus (could go a little higher) and i play metal like trivium and bullet and pantera but i also play some sum 41 stuff. Hit me with some suggestions. is any half stacks or anything in my price range.
are you gigging? within that price range a used combo would be much more suitable to your needs, possibly a mesa f-30, jcm800, classic 30, etc..

MIA Fender Stratocaster
Jackson Kelly KE3
Ibanez Universe
Marshall JCM 800
Orange Jim Root Terror
Mesa 2x12
Ovation Custom Balladeer
pedals and such in profile
Most halfstacks under 1500 are crap
You don't need a half stack unless you're playing a stadium
A combo of equal wattage or less wattage will be applicable.
For your budget

B-52 AT 112 combo
Randall RG50TC combo
Bugera 6260 combo
Used Peavey 5150 combo
Used Peavey Ultra combo
Used Peavey XXX combo

Any of those will suit you fine