My advice, and I'm sure I'm not going to be alone here, is just keep trying! I honestly don't think there is much of a difference regarding service with Orbitz and Expedia, though I have had bad experiences with Expedia for Air tickets.
The thing is you can keep checking rates and cancel old reservations if you find a better rate. Also, you can try Hotwire, where they will find discount rates for you, and quote you the price, but you are not automatically booked and locked until you accept the rate (unlike Priceline).
Also, once you get a rate quoted through Orbitz/Travelocity/Expedia/Hotwire, go to that rental car company's website and see if they are offering any special coupons, free upgrades or codes on top of the rates quoted. For that reason I let the search engines on Travelocity etc. do the "sorting" for me, then I go to the three cheapest car companies listed and see how much better I can do.
IMO, It's all part of the fun of planning a Disney vacation, the bargain hunting
Have a fantastic trip and a safe drive, New Jersey neighbor (my dad lives in Barnegat and I'm down in Stone Harbor/Avalon nearly every summer)!