DSLR – Pentax Body

After purchasing a FA 77mm recently for bokeh purposes but have ended playing with it wide open just for narrow depth of field photos; mainly portraits of statues and a few garden shots and I was wondering if the DA 55mm width open will give me a more pronounced out of focus on similar subjects and/or distances as well as good bokeh and sharpness? (can any one post any flower shots with stamens at F1.4 with a Da 55mm/F1.9 with a Fa 43mm?) Or… would I be better off investing money on a FA 31mm? Any advice or thoughts about this would be most welcome as I am actually going NUTS over this for the past 2 weeks and even started to look at lens for my Canon 400D!!!!!!!!!!!!!! (ps I’m looking at a AF lens and yes I have read most of the posts about 50mm lens and bokeh… etc and have just recently got a FA 1.4 50mm but it is a bit soft – I also find that the 77mm just doesn’t take a bad photo and maybe I’m hoping the 31 or 43 may be the same!)