My priorities are:

1. Above average to excellent taste, favoring sweet and complex types right off the tree without needing cold storage.
2. Varieties that are known to be productive and dependable. (Thus ruling out Ashmead's Kernel and Rubinette) Also ruling out smallish size varieties.
3. Varieties that are not overly difficult to grow or that require extra sprays. (Told my friend he will be spraying at least 6 times a season)

Here is initial list of possibilities I have come up with so far.

summer- early season: Sansa
early fall: Crimson Crisp
fall: Grimes Golden, and/or - Kidds Orange Red, Suncrisp, White Winter Pearmain, or Roxbury Russett
late fall: Goldrush

I am reading conflicting articles that Grimes Golden needs cold storage for best taste so not sure about that one.
Most of these seem to be dependable types but I am just not sure if they are dependable here in the deep south.

I am near Atlanta close to the 7b/8a zone line, thanks for your help, Chris.

I got my first few Crimson Crisp apples this year and they are pretty sharp/acidic. I picked the 2nd on September 1st and while it was 12.2-14.7 brix and the seeds were black, I don't think it was fully ripe. I was saving the last apple on the tree to ripen a bit more, but it disappeared a few days later. Maybe if they hang a long time, they will sweeten up, but at that point it won't be an early fall apple anymore.

I would suggest Sweet Sixteen as a good early fall apple, as it has great flavor and decent disease resistance. But I'm not sure how it would do that far South (it's from Minnesota). It also took the year off for me in 2014, so that is another strike against it.

Kidds Orange Red is definitely tasty and productive (it was the only tree this year which broke a branch due to fruit load). One caution is that it goes from perfect to mushy very quickly. I'm not sure how it would hold up in the South. Maybe it can be positioned in the row so that it gets shaded a bit during mid-day from one of the other trees?

For season extension, Williams Pride would give you an extra 2-3 weeks (early August here, maybe late July for you?). It isn't a sweet apple, but has a pretty good balanced flavor. According to Kuffel Creek in Southern CA, WP takes the heat very well.

Another they mention that you may want to consider is King David. I don't have it, but remember reading that it has resistance to all 4 major apple issues.

I picked exactly one Sansa this year. It is a 2nd leaf tree, which produced at least half a dozen apples. But, they proved popular with the animals, so I broke down and picked the last one on 8/10. It wasn't ripe (white seeds and 12.5 brix), but still had a nice sweet flavor.

Have you thought about any old Southern varieties like Aunt Rachel or Limbertwig? I don't have personal experience with them, but it seems like places like Century Farms would have some good knowledge. Now that I'm looking, I feel the need to place a small order...

Think Lawson's Nursery in Ball Ground has closed - Mr. Lawson was getting well up in years last time I heard from him; would be a really good reference for varieties that will do well in your area.
Have seen good reviews on Johnson Nursery in Ellijay - looking at their website, I see some stuff, like Cox Orange that probably won't work for you - but maybe if you actually call and talk to someone... they can give you the skinny.

I went crazy planting old and 'antique' varieties when I got started; they all sounded so good! A trusted friend who was in the fruit nursery business for decades opined that some of those antique/lost/extinct varieties fell out of favor for good reason... Word.

Anyone growing Pixie Crunch out there? I have read that it is small but sweet.

I grafted MonArk last spring, I am looking forward to trying that one as well.

I noticed that CF lists King David, so it must be pretty well adapted for your area. Cummins has it on G41, so it could work.

I was growing a potted Pixie Crunch on M27, but borers killed it this summer, before it could produce fruit. I didn't even realize they were attacking it until I passed it by and saw the trunk cut off about 1 foot in the air.