People must get sick of hearing this, but you should try the DeepDiscountDVD.com 20% off sale which should happen Novemberish. Also try checking the selection of used DVDs at Wherehouse.com and use the code ISC409OF.
DDD has no shipping or sales tax. Wherehouse has sales tax, and shipping is $2.95 for first item and $1.00 each additional item (although it might be less, their rates have been lower on some recent orders). Hope you find some good deals. Personally I plan on getting the Wrestlemania set from DDD once they have their sale.