Jim,
If you have had the opportunity to play Dallas National, then you probably have the means to play the other "exclusive" DFW metroplex courses. That in mind, and assuming you want to stay relatively close to downtown Dallas, I would suggest trying to get on Preston Trails, Brook Hollow, Lakewood, or Northwood. While a bit of a drive, Vaquero (north of Fort Worth) is getting rave reviews. Those I know who have played it say the reviews don't tell even half the story. If you can swing it, and need a fourth, give me a shout!! Just kidding, sort of.
Regarding Dallas Athletic Club, it has been a while since I played out there. But, they have recently renovated both their courses, and I have heard good things. In fact, I am seriously considering joining there, so if you do play, I would appreciate your post-round thoughts.
Have a good time in Dallas.
-Jason