Sleep Ez is dunlop or talalay blend, again, which and why

I have to also figure out return policies, costs, etc...i will call them monday morning once i know what i want...i also dont know what firmness to get, putting over new spring bed, which is slightly too soft for lower back, so i need support or firmness but not too much, i have had a latex bed before and too much is awful...what do i want there too?  i know, tough one