Thanks for all the advice, but I have done it all. Got the best thermal paste and applied as shown on their website in a very thin layer.

Yesterday I reached 59C with system temperature around 43C (after one hour of 45% load, ambient temperature 20C). On a hotter day the temperatures may be higher. What's your sys temp for comparison? The noise reduction may raise the temperature somewhat, but as stated I added extra fans, one intake and one exhaust.