Hi ChristinaM,
It’s fortunate that your warranty claim was approved but not so fortunate that you are limited to the mattresses sold at Sleepy’s.
Post #66 here and a couple of other threads it links to includes some discussions with forum members in similar circumstances (also limited to lower quality/value choices at a chain store) and may be helpful.
One other piece of good news is that Sleepy’s has a good selection of latex, memory foam, and gel memory foam toppers so you can test various mattress/topper combinations in person … assuming they will let you exchange for a mattress topper combination instead of just another mattress … but even if they don’t you can get a good idea of how a particular mattress/topper combination will feel perform and then purchase a similar topper elsewhere for a lower price.
Phoenix