Since one month and a half my loop is like this: res->pump->block->double rad->single rad->res
In my case it was far better than one single rad, i won more than 8-10ºC with both together (back-to-back) in front to the usual 4-6ºC you're used to see when you change from a single to a double rad, and maybe i could run a cpu + gpu block's when i improve my pump.
Here's how i planned the loop:
The result with the new P45 mobo (i have to clean it all a lil bit as well as manage better the cables but this mobo is not the best for that, at least the "Pro" version):
