I replaced my 15 year old Tempur mattress with a Simba Luxe about a year ago.
Like you I had lower back issues and I'd wake up every morning stiff as a board and aching like I'd been run over by a tank in my sleep.
Now, the back pain is pretty much a thing of the past, and I sleep like a log.
I do religiously turn the mattress over once a month, although the guideline is once every 6 months after the first three, I believe.
They also threw in 2 pillows, a mattress protector and a duvet, as well as a 12-month interest free payment option.
Overall, I am very happy with it.