Fren... i'm no engineer but u can use the loop that u have, & zahri is right.
The water won't be distributed evenly as the gpu block doesn't restrict water too
much, & the cpu block needs high volume flow to keep cool. May i suggest
restricting water flow to the gpu by adding a smaller hose of a valve, clamp the
hose or by other means. By this more fluid will flow thru the cpu block but make
sure u don't restrict by too much as to cause the gpu to run at high temps. I MAY
BE WRONG!! Discuss with others before attemping this as it may not work. It's
only my 2 cents.