Hi sashay,
The first thing I would suggest is to read this article which will help you avoid most of the lower quality and value mattresses that are sold by most of the largest brands and mass market outlets.
The tutorial post here has a step by step process that will greatly increase your odds of finding the best possible mattress that will fit your needs and preferences in both the short and long term and will help you connect and recognize the “experts” with the experience and knowledge in your area that can help you make much better choices.
You can see the quality specs of the Apple Valley mattress here (click on the “specs” tab)
Comfort Type - Memory Foam
Support Layer - 6" foam 28 ild 1.5lb
Comfort Layers - 2" memory foam 2.5lb
Mattress Height - 8"
As you can see … it uses some very low quality foam. 2.5 lb memory foam is close to the worst density/quality memory foam you can find anywhere and 1.5 lb density base polyfoam is also on the lower end of the spectrum but may be more appropriate in this budget range.
You can also see the quality of the materials used in the iComfort line and some thoughts about them in post #11 here. They use lower quality materials than I would consider in a mattress in this price range.
Post #2 here has a list of the better factory direct manufacturers and retail stores that I’m aware of in the Austin area.
Hope this helps 
Phoenix