Hi Liquidtheguy,
The better options and possibilities I’m aware of in the Philadelphia area are listed in post #4 here and there are several where you would be able to test different types of latex and latex mattresses.
OK … I understand what you meant now 
There isn’t a firm section or divider line in the center (you may be thinking about some airbeds that have this) but there would be a transition in the middle between any different firmness levels on each side (which of course is the reason for having different firmness levels in the first place). The “feel” of the transition would be reduced by the soft layer on top and the quilted cover which would make it more gradual and less obvious but the bigger the difference between each side the more likely you would be to notice it if you slept in the middle of the mattress. There is more about the pros and cons of split layers (mostly pros) in post #2 here.
Phoenix