How to approach seller of damaged amp

I received amp via Fedex damaged, but the packing is poor at best, flimsy box, amp covered with plastic grocery store bag and a piece of cardboard on top and bottom. Now I am sure this does not meet Fedex packing standards (deny claim) and I feel the seller shares some responsibility. Ideas? I would just like to return (i abosrb shipping cost and seller sends $$$ back) it and null the deal does this seem equitable?