I've had your Simba / Emma, both sunk after a few months. Actually opened one up and realised the build quality is terrible. Then I got a tempur mattress, had it for over 5 years and it's as good as when I first got it. Superb quality, doesn't sink. I too had lower back issues and now not so much. It's pricier for sure. Just go onto your local Dreams and sleep on one. I even use their pillows (Tempur that is)