Hi pickamattress,
I would be very careful about using ILD specs as a basis for comparison because ILD is only one of several factors that is part of how soft or firm a layer or a mattress will feel (see post #4 here). ILD ratings are also not directly comparable between different types of latex or between different types of foam (see post #6 here).
The most effective way to know whether a particular combination of layers and components (including the cover and quilting materials which can have a significant effect on the feel and performance of a mattress) is a good match for you is with your own personal testing where your body will tell you how firm or soft and pressure relieving and supportive a mattress feels for you. If you can’t test a mattress before a purchase then a more detailed conversation with a knowledgeable and experienced manufacturer or retailer that has your best interests at heart and where they can help “talk you through” which of their mattresses may be the best match for you is the next best approach (see mattress firmness/comfort levels in post #2 here). In this case the return or exchange options that are available to you after a purchase would also become a more important part your personal value equation and the risk and “value” of your purchase.
Most “should I” questions are about personal preference and where in the range of risk you are most comfortable and all the other pros and cons involved with each choice. There is more about the pros and cons of a local purchase vs an online purchase in general in this topic. For those that are comfortable with the additional risks of an online purchase (and the risk would also depend on the return or exchange options) there are certainly some very good online options available (including the links to the online lists in the tutorial post) but these are the types of questions that only each person can decide for themselves based on the specific mattresses they are comparing.
Phoenix