Usually a Saturday night stay improves the fare.
With your days, you're looking at ATA for $268 which I would say isn't too
If you can arrive on Saturday night the 8th instead of Sunday you'll save maybe around $20 it looks like this time and you can fly on AA (TW) or NW.
My strategy includes looking at Yahoo! and Orbitz and then seeing if the same fares are available at the airlines' websites. If all else fails I'll try Hotwire which can give you good fares but not all the time. You can't get FF miles if you use Hotwire though.
Hotwire can get you $239 RT total after taxes if you fly the 8th-13th but Hotwire's catch is that you don't know the airline or flight times. Kind of exciting actually since you don't know the variables of your trip. I've pulled the Hotwire slot machine handle a few times
. There's also Priceline but I haven't used them.
The other option I look into is driving to nearby cities. Can you make the 3 hour drive to KC? Or 2 hour drive to Omaha?
How many people are going on this trip? If there's two of you, WN has friends fly free where 2 people can go MCI-MCO for $278 round trip on the dates you want! $289 from OMA on the same dates. If single traveler the fares aren't too great though.