Hi gabodi,
In a perfect world then yes. But unfortunately all of us aren’t in a position that we are able to buy the type of mattress we would buy if money was no object. In these cases there are tradeoffs involved in deciding how close to our “ideal” we can come within our budget.
While latex makes a very supportive, conforming, and durable support core … high quality polyfoam in a support core can also be very durable. Tempurpedic mattresses for example uses a high quality polyfoam in their memory foam mattresses and for most people … if they choose the best one for their needs and preferences (or any mattress that uses similar quality materials) … they will last a long time. The weak link of almost all mattresses will be in the uupper layers of a mattress and this is where more durable materials are most important. Some people may even be surprised to find that they actually prefer the feel of an innerspring or even in some cases a high quality polyfoam support core with latex on top even though by most standards latex is a “better” and higher quality material. In other cases, some people may not even be able to tell the difference between a latex/high quality polyfoam hybrid and an all latex mattress and may not be willing to pay for something they can’t feel or where the benefits of a latex core aren’t as important to them as having it in a comfort layer. In other cases yet … they may find that they prefer a high quality slow response material like memory foam.
Because a mattress is one of the most important household items that we can purchase and arguably has a bigger effect on our wellbeing than any other household purchase … I generally suggest that people choose the best quality and value they can in any material or component within their budget limitations. Using a material though that has benefits that can’t be felt or where it’s strengths may not be as important may also not be a good choice.
All materials come in high and low quality versions … including polyfoam … so the goal is first to find out which types of materials you prefer and know the benefits of each material … both that you can feel and that may be important to you over time. Once you know this … then the next goal is to choose the best quality /durability of this material that is possible inside your budget.
While any material can meet our needs (pressure relief and alignment) in the right combinations and quality (no matter what someone’s weight) … they may not all meet every one of our preferences or the things that we may not notice in a showroom but will become apparent over time when you actually sleep on the mattress.
So the first step is to find out how latex feels compared to polyfoam and memory foam in the comfort layers and also test to see if you can feel the differences between different types of support cores (innerspring, latex, polyfoam) so that you have a sense of how each material feels and performs for you. Then you can add the properties of each material such as durability and breathability and sleeping temperature that you may not be able to know for sure in your short time in a showroom. Once you’ve done this … then you can look at your options to decide which mattress and which outlet can offer you the best possible combination that will suit your needs and preferences and is also inside your budget.
This would depend to some degree on the amount and layering of the latex and also on what other components were included (such as the quality of the cover and the quilting). In a 6" latex mattress this would be no problem but it’s unlikely that 6" would be enough for your weight. In an 8" or 9" latex mattress … you are a few hundred below the normal low end of an all latex king size mattress once everything is taken into account and you would still have to make some tradeoffs. Many people of your weight would also prefer a thicker mattress in a range up to about 12" (which has a greater range of compression from soft to firm) and this would be well out of your $1500 budget. Don’t forget too that this is “mattress only” and that you will need a foundation or bed for the mattress as well which will add to the cost if what you have isn’t suitable.
A list of the members here that specialize in working with their customers online or “on the phone” and sell great quality and value mattresses are in post #21 here. These are generally among the best value you will find in the country. Many of these make all latex mattresses with different features and benefits in different price ranges. don’t forget too that all of them offer either a 5% discount or a bonus with a mattress purchase to members of the forum which can help a little with your budget.
So for now … I would focus on “flopping around” (checking how it feels when you move) … lying around (checking how it feels when you are completely relaxed or with very slow and lazy movements) and maybe even taking a nap on a few all latex , and latex hybrids and a few other combinations in your “playground” (any store and mattress in the area where you can find out what is in it) just to experience the general feel of different combinations of materials and components. Once you’ve done this … then is the time to begin narrowing down your choices to get as close as you can to your “ideal” inside your budget either with a local purchase (if the value of a local purchase that you can accurately test justifies any extra cost) or online (if a lower cost justifies the greater risk of buying something you can’t try first).
One step at a time 
Phoenix