Topper for Origins Pocket 1500

We bought the origins pocket 1500 with an ottoman base in the spring and after 3months we (me 16st her 9st) feel it’s on the firm side of medium although miles better than our previous beds.
We would like to soften the feel with a suitable topper but need some advice on what material to buy that would complement The mattress and base I.e. natural fibre (feather), memory foam or latex
Thanks