You will see the drop Rubix mentioned, if your loop has the power then theres no reason your Gpu's won't be at the same temps as your cpu as well
What raddage were you planning on for the Cpu/gpu? Overclocked or stock?
Things like this are covered in the , yep you guessed it, sticky :-)
Work out your TDP, calculate the necessary rad for that, then add another 360 to get some good clearance
Well, one of my CPU's cores were maxed out during the test.