Just got back from CV and SY Kmarts. Both are out of $20 PSN cards (unfortunately I took last 3, sorry). Chaining the cards together does work i.e. one card per transaction to get the $10 coupon. However both stores have a some $50 cards with the $20 coupon.
CV kmart had a couple DJ Hero bundles (PS3) which are supposed to be $39.99 clearance.