There's no way you can fit all those segments into a single day. Further, DL fares generally only allow for one-stop (or zero on routes where there is significant non-stop flights). You can't expect to add a bunch of stops and keep it on a single fare. It just doesn't work that way. RDU-DEN fares only allow a single stop and the valid routes are ATL/JFK/LGA/DTW/MSP/SLC. Of course, just because a route is valid doesn't mean there is going to be fare bucket inventory on it in the cheaper fare classes on a given day. For the dates and price range you have given. RDU-DTW-DEN-JFK-RDU looks to be about the best you can do for $489 and 3775 MQM's. I assume the $500 price is for roundtrip and not each way.