Hi bob.hawk,
SleepEz is a member of this site which means I believe they provide among the best quality, value, and service in the country. There are many members who have purchased one of their mattresses and a forum search on SleepEz (you can just click this) will bring up hundreds of posts with feedback and member’s experiences with them.
Green Mattress Factory / Dremata is another matter completely. I would be very very cautious here.
Before considering making any purchase from them or any of their other sites … I would do a little digging into their history so you can make a more informed decision about them. Post #2 here and the post and other online information it links to would be the best place to start before making any purchase from any of their sites.
Hope this helps
Phoenix