Hi jlyr3mixed,
You can see some comments about Memory Foam Solutions and Allsleep in post #2 here and post #12 here and post #2 here and in post #14 here. As you can see there are many red flags here and I would be very cautious about the accuracy of their listings and the “real” quality/density of their memory foam based on their history over the years.
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 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 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 (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists.
Since the most important part of the value of a mattress purchase is PPP and how well you sleep on a mattress … it’s important to make sure that a mattress is a good “match” for your body type, sleeping style, and preferences and one of the issues in dealing with an online retailer that is part of what I call the “race to the bottom” is that they are generally more interested in selling you anything that you are willing to buy rather than educating you about whether a mattress that will be the best match for you. This can be very risky because they are also well aware that if you don’t like the mattress that you can’t re-compress it and ship it through a courier so they need to be returned with a common carrier and the cost of returning it can often be more than the cost of the mattress itself so they have little risk of comfort or warranty returns regardless of how their customers like the mattress or how long it may hold up because of the quality of the materials they use.
In many cases … the knowledge, experience, and guidance of the manufacturer or retailer you are dealing with can be one of the most important parts of a successful mattress purchase (unless you are one of the fortunate few that can sleep on anything at all without any discomfort or “symptoms” that can come from sleeping on a mattress that isn’t suitable for you and the quality and durability of a mattress isn’t an important issue for you).
Some of the better lower budget online options I’m aware of are listed in post #4 here but again … if your maximum budget is only $300 (which would generally be suitable for a guest mattress or a mattress that is only for temporary use or perhaps for a child) it may be worth avoiding memory foam completely because it’s very unlikely that you will find any good quality memory foam mattresses in your budget range (see this article) and it may be worthwhile considering other types of materials and mattresses (innersprings and polyfoam for example) where you may be able to find higher quality and more durable materials in your budget range.
If you let me know your city or zip code I’d also be happy to let you know about any of the better local options or possibilities I’m aware of because there may also be some local options that are also worth considering.
Overall … you are in a budget range where it isn’t realistic to expect that you can buy a good quality memory foam mattress and with the mattress you are considering I would also say you are deep into “buyer beware” territory.
Phoenix