Question about numbersFollow

So I just dinged 40 and I'm trying to decide whether to drop my Robe of the Lich for the Dreamweave Robes. My question is this, what are the numbers for Int+ = Spell dmg? Like, how much Intellect = How much spell damage? Also, how much Intellect = How much Crit chance for spells? I've always wondered this but never found the info. Forgive me if this has been posted elsewhere.