We use AA Ohio and their prices are better than Undercover Tourist.
While I like the idea to buy from Orbitz because of their Buy 3-days-get-5-day deal, but that's only on a Hopper ticket, so you'll be paying $341.87 (Adult) and
$322.70 (Child) and then have to add one day to your ticket once you're at WDW (just under $40 per person).
A regular 6-day base ticket without hopper is $318.41 (Adult) and $298.22 (Child), so you'd be overpaying if buying the Orbitz deal, even if you count in the 10% rebate via Ebates.
Your best bet is to check your local AAA office, and if they sell discounted physical tickets, buy your tickets from them. For 6 tickets, you'll probably save around $30, so you need to figure out how long it'll take for the $30 savings. Otherwise, I'd just buy the tickets straight from Disney.
Just my 2 cents.