Hi all;
I need some advice in choosing the right mattress to rectify my back pain. About my posture;

tall guy: > 190cm
posture: abit slouching to the front and abit to the right.
size: moderate to big size
(will grow wider in the future due to intensive body building)
type of bed: queen size (tried sleeping on a super single bed at Harvey Norman but end up falling down on to the floor when turning over) ~ SERIOUS !

Currently, i am being advised by the sales assistant at Harvey Norman that i should try sleeping on a firm bed to reduce my back pain. He keeps pushing me the Hilker Gomez. I tried it and felt it is ok.

Hence, do you guys have any advice? Also, how about the brand Tempur? is it good for posture/ reduce back pain?