Sorry, I didn't make that very clear. I don't really want an IRON bed. Definitely going with the upholstered bed, just so many choices.

You could have a frame made that is the same height as the divider in your current bed. then put the Casper solid foundation on top of the newly level existing bed.

I wouldn't bother with an upholstered bed, just have a frame and then a headboard, perhaps an upholstered one that will give warmth and softness. Upholstered beds may be too trendy, something that will look out of style in the future, although if you have your heart set on one then by all means. It's easier to keep it simple and just focus on the headboard and bedding to create the bed of your dreams.

As others have posted, you can just use a headboard attached to a frame unless you want the specific look of side rails and foot board.

I found the selection of upholstered beds/frames to be quite limited when I looked last year unless I wanted a gray or beige headboard.

You can have a headboard made custom relatively inexpensively and then the universe of fabrics is available and you can get exactly the style you want as well.

That's really frustrating! Below is a link to Ethan Allen's platform beds. There are many custom options for you, including nailhead trim, diamond or boxed tufting or smooth finish, platform beds with or without storage underneath, wood finishes (when applicable), contrasting piping, thousands of fabrics and a hundred leathers to choose from, and working one on one with a designer to complete the details of your new bed. Let me know how I can help, through Ethan Allen's gorgeous offerings. Otherwise good luck!

https://www.ethanallen.com/en_US/shop-furniture-bedroom-beds?prefn1=type&prefv1=Upholstered%7CPlatform