Hi Thinkink,
The first place I would start your research is the mattress shopping tutorial here which has 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 more 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 buy a suitable mattress 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 that are involved in each of them 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 comparisons between mattresses in terms of suitability, durability, and value.
I’m not sure where you are in the SE PA area but the better options or possibilities I’m aware of in the the Philadelphia/Wilmington/Trenton areas (subject to the “vaalue” guidelines I linked) are listed in post #4 here. There is also a list for the Harrisburg area in post #2 here and the list for the Allentown/Bethlehem/Easton/ Lehigh Valley area is in post #6 here.
The mattress shopping tutorial also includes two links to the better online options I’m aware of (in the optional online step) and one of them is for memory foam mattresses.
I I would be very cautious about using other people’s reviews or experiences on a mattress (either positive or negative) as a reliable source of information or guidance about how suitable a mattress may be for you or the durability of a mattress and in many cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person may be completely unsuitable for someone else to sleep on or vice versa (see post #13 here).
The Dynasty is made in China which means that the quality/durability of the materials are more uncertain than materials that are made in North America and it’s durability could also be affected by any fillers that are used in the foam or how long the mattress was compressed during shipping and storage (see post #6 here).
You can read more about Dynasty in posts #3 and #4 here and a forum search on dynasty (you can just click the link) will bring up more information and feedback about them as well.
You can read more about Casper and Leesa and some of the other new “one choice fits all” mattresses that only have a single firmness choice in post #3 here.
Novosbed used good quality and durable materials in their mattresses and they are one of the better online memory foam sources which is why I included them in the online memory foam list. A forum search on Novosbed (you can just click the link) will bring up almost 400 forum posts that mention them although of course only some of them are feedback from people who have purchased them.
NOTE ADDED JAN, 2016: They have now introduced their new simplified choice mattress which has replaced their previous models and have also become a member of this site.
While there are too many unknowns, variables, and personal preferences involved for anyone to be able to tell you which mattress to choose … hopefully the information here can help with “how” to make the best possible choice and I’m looking forward to finding out what you end up deciding … and of course any other comments or questions you may have along the way.
Phoenix