Why are you so certain you want a memory foam mattress? Surely the question should be this is what I'm looking for in a mattress does any one have any suggestions (memory foam or not)?
Having recently bought a new mattress I would recommend farming out the kids (if needed) and spending several hours trying several out (if possible with your preferred pillow). Then go back again a week later a try them again before handing over the cash. What is one woman's nirvana is another woman's chronic back pain!