Hi karen,
The iSeries is actually a type of memory foam mattress (or memory foam hybrid) and they all have at least some gel memory foam in the comfort layers along with other types of memory foam, polyfoam, or latex. The innerspring is good quality (and an innerspring wouldn’t be the weak link of a mattress) but the comfort layers in some cases use some very low quality materials. You can see the different types of materials they use in iSeries in the iComfort information in post #11 here. The only iSeries models that don’t use low quality/density 1.35 lb polyfoam (what they call comfort foam and support foam) in the comfort layers are the top 3 models. You can see the layering of each of the models here.
While the top 3 models are the better ones in the line (and the most expensive) … none of the iSeries or any of the major brands would have great value and I would read this article (if you haven’t already) before considering any major brand. the Stearns & Foster “luxury latex” for example uses mostly synthetic latex (the lowest quality and cost type of latex) called “smart latex” and they also have a lot of polyfoam in the upper layers of the mattress. In spite of this … they sell for more than many other mattresses that use much higheer quality latex without the “weak link” of the polyfoam in them. I would also avoid the Ashley which also uses some low quality materials.
Post #155 here includes the factory direct outlets in and around Fayettesville which are the closest to you.
The Raleigh list is in post #6 here.
Charlotte, NC is in post #2 here.
Some of the “possibilities” in the Jacksonville and Wilmington area but would require some further research are in post #5 here.
Post #5 here also has a list of possibilities centered on Morehead City, NC. which would be the closest to you but it doesn’t include any factory direct manufacturers
Phoenix