Considering you're sorcerous, I'd go for Silken Armor.  It's artifact 2, provides 5 lethal and 3 bashing soak, and has optional 2 mote attunement.  (the attunement removes the -1 mobility penalty)  Then you could spend your last artifact dot on a hearthstone necklace.<br/><br/>Of course, if you abandoned the tower mage concept, hearthstone bracers are in general pretty handy.