I think a Dual DDC is the best choice for your loop. Else do this way -
Res > DDC Pump > GPU Block > Rad > Swiftech Apogee with DDC Pump > Rad
This is the best choice and I am sure you will have high flow rates. If none's possible , get a D5.
P.S - Add the 240mm RAD before the 120mm one as it will increase flow rates.