Hi chopsui,
My first suggestion would be to extend the length of time before making your purchase since buying a mattress with a sense of urgency is one of the biggest reasons for buyers remorse.
The first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP (Posture and alignment, Pressure relief, and Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or if you can’t test a mattress in person then your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
The best place to start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that you will need to make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for when you sleep on it in “real life” and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability and PPP (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists (based on all the parts of your personal value equation that are most important to you).
One of the challenges of buying a firm mattress and then adding a topper when you can’t test the mattress/topper combination in person is that choosing a suitable topper that is a good combination for you and the mattress you are using it on (different mattresses will affect the choice of topper that works best for a particular person) that can be almost as challenging as choosing a mattress that doesn’t need a topper in the first place because the only way to know whether the combination will be a good “match” for you will be based on your own personal experience (see post #2 here).
It can also be more costly than just buying a mattress which includes the same materials as the topper as a layer inside the mattress itself and you would be avoiding the risk of having additional materials in your base mattress that you may not need or that may be lower quality foam (that can soften or break down more quickly) or that may be softer than what would be ideal for a transition layer under a softer topper. At the very least I would make sure that the topper has a good exchange or return policy so there would be less risk of buying a mattress that doesn’t turn out as well as you hoped for in combination with your topper. I would also make sure that you can find out all the specifics of the materials inside the base mattress so you can make sure it meets the quality/durability guidelines here and that there are no weak links in the mattress.
Having said that … if you do choose a suitable mattress/topper combination which turns out to be a good “match” for you in terms of PPP (Posture and alignment, Pressure relief, and your Personal preferences) then it does have the advantage of being able to replace just the topper without replacing the entire mattress if it softens or breaks down before the upper foam layers in the mattress (which is likely because a sleeping system will tend to soften or break down from the top layers down) or if your needs or preferences change over time and a topper can also help extend the useful life of a mattress underneath it as well.
Overall though … it can be a fairly risky strategy because you may need to make a few topper exchanges before you find a combination that works well for you.
There is also more about how memory foam compares to latex in post #2 here but the most reliable way to know which types or combinations of materials or which types of mattresses you tend to prefer will be based on your own local testing or personal experience.
I would be cautious about Lucid and I would read post #6 here and post #2 here along with this topic and the posts they link to before considering them. A forum search on Lucid (you can just click the link) will also bring up more information about them as well. At the very least I would make sure that you find out all the information listed in this article about the quality/density of all the layers in any mattress you are considering so you can make sure that there are no lower quality materials or “weak links” in a mattress that would affect the durability and useful life of the mattress.
I would also be very cautious about looking for “cheap” mattresses where you often get less than you believe you are paying for that tend to use lower quality materials, that often don’t list the materials correctly, that don’t provide the kind of guidance that you may need to make a choice that is suitable for you in terms of PPP, or where you may have little recourse after a purchase if the mattress doesn’t turn out to be a suitable choice and I would focus on the “value” of a mattress purchase instead. In many cases the knowledge and experience of the retailer or manufacturer you are dealing with can be among the most important parts of the “value” of a mattress purchase.
If you are looking for an online mattress then the tutorial includes several links to lists of the better online options I’m aware of (in the optional online step).
If you let me know your city or zip code I’d also be happy to let you know about the better options or possibilities i’m aware of in your area as well. (ADDED: I was looking back at your previous posts in 2013 and this reply includes a link to a list of the better options I’m aware of in your area … assuming that you haven’t moved since then).
Phoenix