Hi Sapphire1166,
The first place I would start when you are looking for a new mattress is post #1 here. It has the basic information, steps, and guidelines you will need to make the best possible choices and learn a bit about the different types of mattresses available including latex / polyfoam hybrids like the Ultimate Dreams.
The choice between the support layers of a mattress (such as an innerspring, polyfoam, and latex) is really a personal preference and of course dependent on your budget. In general though … as you can see in post #4 here and the posts it links to … the durability of a mattress has much less to do with the support layers than it does with the comfort layers you choose. At higher weights … the quality and durability of the comfort layers becomes even more important because this will usually be the “weak link” of a mattress and soften and degrade more quickly.
Some of the better options and possibilities in the Raleigh area that I’m aware of are listed in post #6 here. While most of the latex mattresses there will be well above your budget … they can provide some good testing grounds for you to become familiar with the general feel of latex in various firmness levels and types.
A mattress with a foam support core (whether it is polyfoam or latex) usually does best with a firm non flexing foundation not a flexing boxspring (with springs). I don’t know what size you are looking for (which makes a big difference in price) but you can probably find a fairly cheap boxspring at a local mattress store with some phone calls … just make sure it meets the minimum standards and is suitable to maintain the warranty coverage for the mattress you are buying (the manufacturer of the mattress will confirm this).
Phoenix