%attack, stacks with buffs/pots or not?

the guy i was discussing this with, tediliscious or something like that, said it did with stars and item buffs, i plan to test those eventually too, but i am more concerned on how dark aura/echo work in tandem with this now, do they get added to the 6% to make 10% attack (in the case of echo) or they multiply one another or what.

so many BaM's around, and when i need one, not one collaborates.

and echo isn't easy to find unfortunately :S