I cant speak for the quad but the smallest nozzle (4.5mm) will be the best bet no doubt about it. I tested 4.5mm, 6.5mm and 7.5mm nozzles and the bigger ones are not worth the effort IMO. I do believe that Danny made a 5.5mm nozzle at my request but I was not able to test that one as it was never a prototype size. 5.5mm would possibly be a good alternative to those obsessed with system flow rate at the detriment of CPU temps (I never understood this mentality but w/e). The Fuzion with the 4.5mm nozzle is just a bit better in terms of pressure drop than a GTX so in my book the 4.5mm is ideal - and it tests VERY well as you can see. I asked Danny to have a 3.5mm nozzle made for me as there is still too much flow with the Fuzion and the 4.5 mm nozzle in my loop (system NEVER bleeds LOL).