Hi sanjosva,
As you probably know your budget is very low for a good quality mattress but the first place to start your research with any budget is the tutorial post here which has all the basic information, steps, and guidelines that can help you make the best possible choice … and hopefully avoid the worst ones.
If you also need a foundation then it would leave even less room for the mattress and if it’s at all possible I would consider raising your budget somewhat. Of course if that’s not possible then it’s a matter of finding the best possible choice in your budget range.
I’m not so sure I would agree that Serta has a “good name” in many parts of the industry (including this forum) and they are one of the manufacturers that I would tend to avoid (along with the other major brands or any manufacturer that doesn’t provide you with the information you need to make an informed choice).
You can read more about the Serta Apple Valley in post #369 here and while it is a very low cost material … it also uses very low quality materials that I would be hesitant to purchase even in your budget range.
As you will read a mattress is only as good as it’s construction and the quality of the materials inside it and to make any kind of meaningful assessment of a mattress you would need to know the quality of all the layers in the mattress. If you are dealing with a retailer who has little knowledge and isn’t able to tell you what the specs mean if you post them here I’d be happy to make some comments about any specific mattress you are considering. The information you need is the thickness of each layer or component in the mattress and the density of any polyfoam or memory foam in the mattress.
Once you get to step 3 then some of the better options or possibilities I’m aware of in the Atlanta area are listed in post #2 here. I would call the ones that interest you first to make sure they have some good options in your budget range that you can test.
Phoenix