Hi nezzie,
The first place to start when you are starting to look for a new mattress is post #1 here and the information it links to. this is the most important post on the forum and will give you all the basic information you need to know about what to look for and what to avoid both in terms of mattresses and the places that sell them. In about an hour or two you will probably know more than many or even most of the people who sell mattresses (as sad as that may be).
As you will read … nobody can “recommend” a good mattress for someone else because our individual needs and preferences can be very different even if we have a similar body type and sleeping positions to someone else. The best that anyone can do is to help educate someone into how to make a choice that provides them with the two basic needs of every mattress which is comfort/pressure relief and support/spinal alignment in all your sleeping positions. No matter what the quality of the materials that are used in a mattress … something that is “perfect” for one person can be completely unsuitable for another. You can test for what I call PPP (Pressure relief, Posture and alignment, and Personal preferences) in a showroom but you can’t “feel” the quality of a mattress which is what determines how long the comfort and support will last.
As you will also read … who you buy from can be just as important as the mattress that you buy and identifying better local manufacturers and retailers who can both tell you about what is inside their mattresses and educate you about why it may be suitable for you can be one of the most important parts of mattress shopping.
Some of the better options and possibilities in the new York city area are listed in post #2 here and a more “categorized” list with more detailed descriptions of many of them is in post #7 here.
Phoenix