Previously I didn't even check the images as they are huge at 1680X1050, you don't have to view the task manager at full screen as there is a huge amount of white space with nothing on it...
You can also click on the column headings to order the list by A-Z on that column clicking it again reverses the order so you could get away with a much smaller image, see image.
I have to agree with Alan, none of the avast processes after the scan are in anyway considered excessive, and seeing the percentage of physical memory used as 35% I somehow doubt you have 9.1GB of physical ram as that would be what 3.2GB would represent (35%) if you had 9.1GB of physical RAM. So something just doesn't stack up or should that be add up.
How much physical RAM do you have installed ?
Just have a look at my task manager image (XP Pro) and look at the ash/asw entries and I haven't done any scan and also look at the real hogs explorer and firefox.
So I too don't know where you are getting these figures of 2.8 and 3.2 GB from, but according to your own images, the combined total for avast process aren't responsible for these figures.