Hi Blagdaross,
The first place I would start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you make the best possible choice … and know how and why to avoid the worst ones.
In addition to the more general guidelines in the tutorial post … post #3 here has more information that will be helpful for those that are in higher weight ranges as well because you will need firmer layers and more durable materials than those that are in lower weight ranges.
I would be aware that memory foam will tend to sleep warmer than other types of materials so if you tend to sleep hot then memory foam may not be the best choice for you. There is more about the many variables that can affect sleeping temperature in post #2 here.
If you haven’t slept on a memory foam mattress before then I would at least make sure that you have tested a range of memory foam mattresses and spent enough time with them in a showroom to make sure that you are comfortable with how memory foam feels and performs and to make sure that a memory foam mattress is really your preference based on your actual experience.
The Novaform mattress uses 3" of 3 lb memory foam which is a lower quality/density memory foam which I would normally avoid for any weight range but it would be especially risky with your higher weight both in terms of suitability and PPP and in terms of the durability of the mattress. 3 lb memory foam isn’t likely to hold up very well for someone in your weight range. You can also see my thoughts about buying a mattress from Costco in post #4 here.
I would also be very cautious about using reviews (either positive or negative) as a reliable source of information about either the suitability or the durability of a mattress and in many cases they can be more misleading than helpful because a mattress that would be a good choice for one person may be completely unsuitable for someone else to sleep on (see post #13 here).
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 comparisons between mattresses.
There is also more about the different ways to choose a mattress (either locally or online) in post #2 here that can help you identify and minimize the risks involved with each of them.
When you are in higher weight ranges or have other specific needs that are different from the norm I would also put a higher priority on dealing with more knowledgeable and experienced retailers or manufacturers that can give you the kind of guidance that you will need to make a choice that is suitable for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) and that also uses high quality and more durable materials that will hold up under your weight.
The knowledge and experience of who you deal with can sometimes be one of the most important parts of a successful mattress purchase.
If you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of in your area.
Phoenix