From your gear, I would suggest the Chest of Stoicism. You gain Stam, Dodge, Defense, and SBV. You loose two gem slots, but since you have def in them now, you're actually breaking even without the enchant. If you're going to tank, you need at least 490 Def currently, and I believe someone said 520 or 530 defense at 80. For the gem, you may want to either use the +15 Stam (and loose the bonus) or go with the Sovereign Shadowsong Amethyst (+5 Str +7 Stam)
"By Grabthar's Hammer... What a savings"