No arctic silver will not adhere your ram sinks to the chips. You will need the Alumina for that, or any thermal ahesive tape made for that use. And along that line of thought you won't want to use alumina on your CPU, as it will be near impossible to remove after the bond is made.
Oh wow, what a whole 2 or 3°C difference? For that matter, there isn't even that much of a difference between the cheapo stuff from Radio shack and Artic Silver.