If you're just looking for layer feed, I'd recommend seeing what your local mill or farm shop has. It's always better to support the local business than to buy low quality mass produced feed like Purina.
Yes it is good to support your local businesses but in most cases that local mill is buying 80% of there ingredients from the mass producers.
A local mill will by a Base Mix
(from a mass producer) which a supplement designed to be mixed with grain to make a set feed, They carry mass produced feeds, they buy there supplies
(minerals, salt, trace mineral, sodium bicarbonate etc.) from the mass producers.
Really most mills only buy a few grains locally, grains like corn, oats, wheat, soybean etc. and if there supplies and supplier get low they will have grain shipped in.
As far as Purina being low quality it depends on the feed, there Start and Grow, Flock Raiser, and Poultry Layena are low quality feeds but the Purina Wildlife feed is good and is a step above most, also Purina Mills is owned by Land-O-Lakes who puts out Mazuri and is one of the best Exotic Animal feeds you can get, it's used by a lot of zoo and wild life rescue centers because it is good. I myself use Mazuri Game Bird Feed, Carni-Blend
(carnivorous fish pellet), Exotic Canine Diet. Wild Herbivore Diet, and a few other types of there feeds and I cant complain.
I also look at it like this, any chicken feed that does not contain a animal protein in it is a low end feed....
ETA---
Purina also puts out a decent Show Feed.
http://purinamills.com/show-animal-food/
http://wildlife.purinamills.com
http://www.mazuri.com