A quick browse of the internet travel sites show Delta with the fewest connections, and most of the fares fall into the $400 to $500 range. I'm going to say that's about average for that time of year. This is what I recommend to folks that ask me about traveling, and there's probably others on here that travel on an expense account, (Wisconsin Mike?). Do an internet search of airlines that service Providence, RI to Valdosta, GA. Look for the fewest stops and the most frequency. Then, go to that particular airlines web site and do your shopping. Fewer stops=less opportunity for your luggage to have a vacation on it's own.
More frequency= better chance of getting where you wanted to go in case of delay, or cancellation. I would generally say those two points are worth paying a little extra for...."little" being the key word. Travel agents? They can be very helpful, but keep in mind, they have to make money too. Their routing isn't always the most convenient, or cheapest available to the person actually paying for the ticket. It may just be what gets them the most commission. Also, I'm not 100% sure that Southwest Airlines participates in the online fare comparison sites. You may have to go directly to their website. Flexible travel days are a big bonus. +/- a day or two on each end may add up to some real savings. Happy hunting.....and you are wise to start your shopping now. Hope it works out. See you at DSCF.