I too have one of the 8kg, top loader LG models, just recently purchased.
To say I'm bitterly disappointed would be an understatement.

I too purchase mine to take care of all the large loads I was doing. With 4 children and a DH, there is a hell of a lot of washing! However if I do use the full 8kg [which you think is what its designed to do] then the clothes still come out dirty. I now have to cut down to just normal size loads that I was doing in my 6kg.
Great idea about purchasing 2 6kg! Wish I had thought of that.
I am not a front loader fan at all.