Hi hieyemtim,
Just in case you haven’t read it yet … the mattress shopping tutorial here which includes all the basic information, steps, and guidelines you will need to make the best possible choice … and more importantly know how and why to avoid the worst ones. If you follow the steps in the tutorial one at a time you will have the best possible chance of making a successful purchase in terms of suitability, durability, and value.
I’m assuming that you mean IFD or ILD (rather than ISD) but IFD/ILD is a “comfort spec” which only indicates the softness and firmness or a material (which you can feel when you test the mattress anyway) so it’s not an important spec when you test a mattress locally. What you need to make more meaningful comparisons are the “quality specs” that indicate the durability of the materials rather than their softness/firmness…
The specs you listed aren’t complete so it’s not possible to make any meaningful comments about the quality of the materials in the mattress but if you can provide the information listed in this article (including the thickness, type, and blend of any latex layers in the mattress and the thickness and density of any polyfoam layers) and post it on the forum I’d be happy to make some comments about the quality of the materials or the mattress “as a whole” or help identify whether there are any potential “weak links” in its design.
There is also more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful quality/value comparisons between mattresses or the “finalists” that you are comparing (I would normally suggest having more than one “finalist”). Since the value of a mattress purchase is always relative to the other mattresses you are considering or that are available in your area (or online for those that are also including online options in their research), if you only have one “finalist” or don’t have other mattresses that you are using as a reference to compare with then there really isn’t any way to make any meaningful quality/value comparisons either in terms of suitability, durability, or “value” regardless of the price you would be paying for the mattress.
I would keep in mind that the amount of any “discount” that you may be receiving on a mattress either as the result of a sale or “negotiating” can be very misleading because the reference price you are using may be inflated to make the “value” of a sale or the outcome of a “negotiation” look better than it really is (see post #6 here).
Phoenix