That seems high quality for a preview render! I used to use firefly and tthe poser 4 renderer back in Poser 7. Use Vue now for all poser rendering I find the quality much better and faster at rendering (unless there is a vue background, then it takes ages)

 

Great tip - Set render up before bed and put the settings up as far as you dare! then you can get a good 10 hours of rendertime in ;-)