What about AL WB ,
Cu is not that much better if you look at the whole picture.
Heat transfer consist of heat conductivity (material, thickness, coef. :lambda W/mK) and heat transport from one material to fluid (coef. alpha (W/m2K) which is very complex it depends from temp. ,preasure, speed and kind of fluid, gas or vapour that take or give heat to solid wall. It also depend on quality and shape of this surface).
So heat transfer (K) is : 1/K= 1/alpha + thickness/lambda
then heat fluid (W/s) equals Q/t= K*(Temp. diff.)*A ; A=surface(m2) and if we know that alpha for fluids ranges from 2000...4000W/m2K , you can quickly calculate that alpha(surface, turbolence...) is a lot more important than lambda (material).
That's why I'm trying to do AL block that perform equal or better than Cu. Check this thread:
link btw. it weights ~350g