Where to fit the radiator, top or front?

[Alexoferith]

Spec:
X99 Classified
i7-5930K 3.5 GHz with Noctua NH-D9L CPU Cooler with 2 FANs
EVGA SuperNOVA 1300W Gold PSU
Corsair 780T Black Full Tower Case with 1 x 120mm fan at back (out), 1 x 120 fan at top (out), 2 x 120 fans at front (in)
2 x EVGA GTX 1080 Ti FTW3 SLi
32Gb (8 x CMK16GX4M4A2666C15) - running at 2666 Hz using XMP 1
2Tb Samsung 850 EVO SSD
3TB WD Black HD (data)
4TB WD Black HD (Acornis images storage)
LG BluRay writer

FYR. Last night, playing COD WW2 multiplayer, CPU package temp 64 degree max. GPU 1 temp 59 - 63 degree max, GPU 2 temp 39 max (all in Celcius)

I tried to overclock the CPU. My first step was to 3.8. Temp rose to 78 - 83. GPU similar temp. So, I bought an EVGA CLC 240 Liquid/Water CPU Cooler via Amazon. But I just cannot make up my mind where to put the radiator. If I put it at the front, then it will be providing hot air for the two GPU. And if I put it at the top, then I will have warm air from GPUs to cool the radiator. At the moment, all the case fans came with the case, only the top fan is a Noctua fan. There are some Youtube videos saying that it doesn't matter where to put the radiator, provided the case has space for top and front. Because of the 3.5" WD HDs and the blu-ray writer, I am reluctant to remove the 5.25 casing. In any case, I think the 5.25 casing is riveted to the case so I cannot remove it. I have already removed one of the 3.5" casing, leaving the bottom one, but it blocks most of the 2nd front fan. I cannot justify getting another case after spending the money on the two 1080ti cards. So, I appreciate any suggestion or argument. Many thanks for your time and effort in advance.

Edit:
I have also looked at water cooling the GPUs as well but I am a total noob in this field. I have no idea what component to get so though I have used water cooling before but I went for a kit set, so is this time, an EVGA kit set. But if I go down this route, I will have to get a new case. I have been looking at the Thermaltake cube series. But the budget is getting from zero to around £500 now. May as well go for the whole lot, i9-9900k + ASUS Maximus Hero mobo + 32Gb 4200 RAM. ARRRRRrrrrrrrr It took me over 10 months to save for the two 1080ti.

 

[Ninjawithagun]

Mount the radiator on top with the fans pushing or pulling air out the top. The ambient temperature inside the case will be negligible as long as you have positive air pressure from the front fans providing cool air into the front of the case. Another option is to reverse the back case fan so that it blows cool air inside the case and into the top radiator. Overall, the affect of your GPUs exhaust air is minimal as long as you have positive air pressure inside the case. Alternatively, you can run your system with the side case door removed. That's what I do for both my custom watercooled system and back-up gaming system that has an AiO CPU cooler and air cooled RTX2080Ti.

 

[Alexoferith]

Mount the radiator on top with the fans pushing or pulling air out the top. The ambient temperature inside the case will be negligible as long as you have positive air pressure from the front fans providing cool air into the front of the case. Another option is to reverse the back case fan so that it blows cool air inside the case and into the top radiator. Overall, the affect of your GPUs exhaust air is minimal as long as you have positive air pressure inside the case. Alternatively, you can run your system with the side case door removed. That's what I do for both my custom watercooled system and back-up gaming system that has an AiO CPU cooler and air cooled RTX2080Ti.

Thank you very much Ninjawithagun. I have a few more noob questions. I did some basic mathematics. Am I correct to assume that the total air pressure created by the fans is the sum of all the fans? The total air pressure of EVGA is slightly bigger than the front two case fans. So, I will have to do what you suggest that the fan at the back has to be turned around, i.e. take air in rather than out (as present). But what I am worrying about is that due to the 3.5" enclosure for HD at the front bottom, it blocks 2/3 of the 2nd fan at the front. This will reduce the intake pressure but I don't know by how much. And will this be taken care of by turning around the fan at the back?