Update I bought another 6 gig of ram. Upon rendering a 2,897,000,000 polygon image with 30 odd objects , 4 or 5 ecosystems etc

. No noticeable difference in throwing stuff around on screen.

. Render 1 = 6 gigs of ram = 6.34
. Render 2 = 12 gigs of ram = 6.33

ram usage still no more than 5 gig whilst "throwing things around the screen" (I cannot think of a better term!)

Ram usage still no more than 2.9 gig usage whilst rendering.

So there it is anymore than 6 gig is overkill! My ram is going back ;-) had to test the theory out though.