I believe what she meant about them not stacking is that they do not stack with other instruments of their type. Like a troubador's mace won't stack with the epic's mod, or with the mod on a 1 handed horn, for example. You just get the higher mod, as usual. But stacking with other instruments, yes.. I believe the point is to allow us to get an item for each instrument type, so we can wield something other than our epic. So far, though, I don't much care for the idea (the items aren't all that great for the slots, and I'd rather wield my epic - 1 not-so-great item, than 5 not-so-great items). I'd much prefer an epic 2 idea, upgrading the damage/delay, stats, on our epic, maybe boosting the mod to 2.0 or something at the same time...