Hi Usenamoo,
Just in case you haven’t read it yet … the first place to start your research is the tutorial post here which has the basic information, steps, and guidelines that can help you make the best choices … and avoid the worst ones (including chain stores or major brands).
The Serta iSeries are pocket coil / memory foam hybrids although a few of them also include a fairly thin layer of latex. They will be quite different from most latex / pocket coil hybrids.
Some of the better options and possibilities I’m aware of in the New York city area are listed in post #2 here and there is a more categorized list with more detailed descriptions of some of them in post #7 here.
Phoenix