What exactly affect attack power stat

Hi, to be simple i have a sorcerer just like my friend, we have the same level (55)
We have same dps weapons (1 wand 800dps and 1 other hand 800 dps), same intel (230)

Same parangon tree
the only difference is his amulet which have +3% damages and mine doesnt have this damages boost.

BUT, all that said… he has 3000 attack power and i have 2500.

What could possibily make this 500 damage gap ? i’m so confused and i’m getting very nervous about it cause i looked everywhere on every item i have and he has. I cant see anything changeing that much the damages…

no legendary spec either…

Any idea ?