Mattress

So we're in need of a new mattress for our bed. We got out current mattress only a few years ago, when we moved here but we got a knock off of Temperpedic and it was a king size bed and it was really cheap. Initially, it was comfy but as time went on, that is not the case anymore. It's not good on both of our backs. SOOO any one out there have a great mattress that they like? Please, anyone, we're desperate! Thanks :)