often times I find the cheapest prices on delta.com -- better than any of the booking engines.
Use ITA to find the best fare ,then ask delta.com for that fare and book it. Even if the award calendar doesn't work, delta.com is usually pretty good with revenue tickets.
The only exception I know of is booking PHX->MUC it refuses to show connections through anywhere but atlanta, unless you multi-city and force it, then it will fit them in via MSP,DTW and use the correct fare basis.