Hi reckhart,
I think that Everready073’s advice is excellent so there really isn’t much to add.
The most important part of your choice would be testing the equivalent Tempurpedic mattresses to see which one is the best “match” for your body type and sleeping positions. In addition to the link that Everready073 shared … the tutorial post also has some additional links to some guidelines that can help when you are testing mattresses.
With your body type … I would also tend to minimize the use of 4 lb memory foam in favor of higher density more durable memory foam which means I would be very cautious about the Tempurpedic Cloud series or the Cirrus Luxe which all use 4 lb memory foam in the top layer.
Phoenix