Hi tigers007,
Original mattress factory uses good quality materials (and innersprings), are two sided, are transparent about the materials they use, and have good value … but they don’t have any pocket coils. Some of the others in the Minneapolis list do however but which one was best for you would would depend on what type of foam you prefer to use over the pocket coils.
I would personally lean away from buying a separate mattress/topper combination except out of necessity (where you have no other better options) or unless you can test the exact combination you plan to buy in the store. The reason for this is otherwise you will need to go through two separate decision making processes … one to decide on the mattress and a second to decide on which memory foam topper would be most suitable for you on that specific mattress (the topper that is best for you would depend on the specifics of the mattress) and having to make two separate purchases involves much more uncertainty than buying the best possible combination in a single step.
If you do decide to go with the topper / mattress combination I would first buy the mattress and then use your experience on the mattress as a guideline (see post #8 here) to decide on the best topper choice (rather than having a specific topper in mind before you have slept on the mattress). The best option in this case is a mattress with thinner and firmer comfort layers (using high quality materials) than you would normally be comfortable with so that with the addition of the topper you have the best possible combination. If you choose a mattress with comfort layers that are already “comfortable” for you then the addition of a softer topper could end up having comfort layers that were too thick and soft and would increase the risk of alignment issues on the mattress.
Phoenix