Hi flybear,
The first place to start your research and comparisons is the tutorial post here which has all the basic information, steps, and guidelines you will find most helpful.
If you let me know your city or zip code I’d be happy to let you know of any of the local retailers or manufacturers I’m aware of that would be worth calling to see if they have any mattresses that may be similar in design, performance, or feel to the Tempurpedic Cloud Supreme that you could test in person to see how closely they match based on your own perceptions and experience.
There is also a list of some of the better online memory foam manufacturers and retailers in post #12 here and several of these also make mattresses that use the Tempurpedic Cloud Supreme as a reference point (including Brooklyn Bedding … thanks Visci0usx :)). There is more in post #9 here about the different ways that one mattress can “match” another one.
Phoenix