A lot of people here will denigrate the idea, but since you are in RDU, you should look at Southwest.

Get 100 credits in a year (you can greatly augment the total with credit cards, hotels, and rental cars) and you can take a companion free for a year, even when you are traveling on a reward ticket.

Best deal out there, IMO. Come over to the Southwest fourm here on Flyertalk and take a look.