I think you will like Caye Caulker. It is much smaller than Coz, but far, far, far, far, far less touristy. The Iguana Reef Inn was damaged by Keith but should be back in shape soon. It is a very nice place, probably the nicest on this budget island, though it is on the back side of the island rather than on the sea side.
I would think you can do a lot better than $495 out of Dallas. Fares to Belize are higher than to Coz or Cancun, but DFW is an American gateway to BZE, so keep checking for deals.
--Lan Sluder
Belize First Magazine
http://www.turq.com/belizefirst/