@ por100pre1
Well if you can't take the word of one of the development team I don't know how you can believe more complex issues. I have rarely worried about RAM use from the days I left win9X behind, XP is much better at managing it and RAM is there to be used. avast is far lighter than many other AVs which is shown in the fact that it still supports and can run on the likes of win95 with low RAM installed and that is much more troubled with system resources.
I have been using avast for quite some time now and I see the developments and improvements and on each and every program update the team have tried to further tweak and optimise the program, reducing RAM use and speeding boot and scans, etc. That is their goal and unfortunately windows Task Manager really isn't that good at displaying RAM used you only have to look at the number of memory columns you can look at. There are probably other more accurate RAM use tools out there.