Softer feeling mattress for 22st man and 12st woman

I am looking for a softer feeling mattress as I tend to sleep on my side and front.
Our previous mattress was very firm and neither of us was ever comfortable on it. We changed it for a slightly less firm one and although I found it ok, it still isn't as soft as either I or my partner would prefer.
I like the sound of the hybrid or foam mattresses as I think these would give us the comfort we're looking for although I know that the weight consideration may rule these out.
Price isn't too much of an issue, would just like to know if I'm wasting my time thinking about the hybrids/foam or should I just look at the Artisan ?