Do magical armor enhancement bonuses increase the maximum DEX mod allowed for an armor?
If so, awesome! If not, are there other ways to optimize AC through a DEX driven character?
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The magical enhancement bonuses on armor do not affect the Maximum Dexterity Bonus (MDB) the armor has.
There are a couple of ways to get a better MDB.
Special materials for example. Darkleaf and Mithril both allow another +2 to MDB for armors made from those substances.
You could also look at Combat Expertise which will trade off Attack bonuses for Dodge bonuses. Fighting defensively also works with the trade of sacrificed Attack for Dodge bonuses. Not strictly speaking just for Dexterity high characters... more for BAB high characters.
I won't re-iterate the other (high-quality) answer, but I will note a few additional things to keep in mind:
Armor training lets you add another +4 to maximum dex, as well as reducing Armor Check penalty by as much. It also lets you wear Medium and Heavy armor without speed reduction at levels 3 and 7 respectively.
For example, the Celestial Armor has a maximum Dexterity bonus of +8. It also starts off with a 6 base armor bonus and +3 Enhancement. It's an excellent choice for characters having/expecting to get high Dexterity bonuses. If you have 20+ Dexterity, it's strictly superior to Full Plate. 24+ Dexterity will make it superior to Mithral Full Plate.
Given sufficient Dex, it will beat everything under normal circumstances (though if you have 40 or more Dexterity, armors like Ceremonial Silk without Dex cap can outpace it.)
I found the RPGBot guide on this to be some excellent reading. He also does some of the math, if you're into that sort of thing.