Hi Josephine,
The first place I would start your research is the the tutorial post here which has all the basic information, steps, and guidelines that can help you make the best possible choices … and know how to avoid the worst ones.
Select Foam and Dreamfoam certainly have some good quality/value options but the Night Therapy Elite isn’t a mattress I would consider because of the use of lower quality less durable memory foam (Post #10 here has some guidelines I would use for a memory foam mattress). Some of the better online memory foam manufacturers I’m aware of (including Select Foam and Dreamfoam) are listed in post #12 here.
If you have done some careful and objective testing (using the testing guidelines in the tutorial post) and the Rhapsody was the best match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences), then I would be looking at online memory foam options that legitimately compare themselves to the Rhapsody. Several manufacturers on the list make a mattress that uses the Rhapsody as a reference point for comparison and post #9 here has more about matching one mattress to another that you can use for reference when you are talking with online manufacturers or retailers.
Phoenix