IMO, Good+ mattresses are $1K and over (discounted). I think a good brand to me may turn into a bad one for you (i.e., your body vs. my body require different stuff).
Whatever you end up doing, choose well and don't be a tight wad as.....
1/3 of your life will be spent in bed.
I am still young and a tiger......I spend more than 1/3 of my life (not alone) in bed.