Origins Pocket Latex 1500

Hi,
I currently own an eve mattress (in trial period) and I am finding it is giving me terrible back and joint pain. I go to sleep on my side, and usually end up on my back. I am finding with the eve that the first comfort layer is too firm, resulting in pressure on my shoulder and hips on my side and on my shoulder blades when I am on my back. It seems to "fold" rather than sink, which feels like it increases the pressure. To be honest it is neither comfortable when I go to bed, during the night or when I wake up.
Previously I had a leesa mattress, which felt great when I first lay down, and slept nice and cool (man made latex top), but was too soft over the course of the night, resulting in bowing/sagging.
Im considering your pocket latex 1500 - I like latex as it is much cooler than memory foam and doesnt have the sinking feeling (so I get stuck in a groove all night, unable to turn) - the springs should help with this as well. I have never liked "plush mattresses" or anything with large divets/quilting in the top. Do you think I'm heading down the right track? If I purchased this in firm, would it be more like a medium firm with the latex top?
I am about 65 kilos/177m tall - partner of similar weight & height. Bed is slatted, super king.