Does RAM cooling Heat Spreaders accutally cool the RAM? If so approximatly by how many degree celcius?

How many degrees is hard to say it depend on your case cooling and ambient temperature, but it can make overal cooling of memory chips much better.
I am using Corsair Dominator memory modules (probably one of best memory cooling) and comparable to my old modules they went from very hot to just warm over 15° diference, but i have board where memory modules are quite close to each other.

thanks..

A good addition that gives some real help in ram cooling is this, as reviewed by jonnyguru:

http://www.jonnyguru.com/modules.p [...] ry&reid=56

Its not exactly what you asked about, but it does tell that good ram colling is available at a reasonable price.

thanks again...