[charliehorse55]

I have a single 480 radiator in my 800D and I love it. I think with your loop a thick single 480 radiator would give you enough cooling power without having to mod the bottom. If you just mod the bottom to mount a 240 radiator horizontally the air it sucks in will be warmed before going through the 480, making it almost useless. The correct way to mod the bottom is to cut holes in the side of the case for exhaust to allow for the hot air from the 240mm radiator to be exhausted out the side of the case before it can interfere with the 480.

I would let the pump run power all of the time, however if the noise bothers you hooking it up to the CPU PWM header is a good way to have it automatically controlled.

 

[charliehorse55]

I used an XSPC RX480 radiator in my 800D and it's top mounted. I cut out the existing grill with a jigsaw and lengthened it as well. I then installed a radiator grill and used that to mount the radiator.

Here is a nice post that shows how to mod for a 480 and how to properly position a 240:

http://www.overclock.net/computer-ca...ml#post9437823

Here's another view:
http://www.overclock.net/case-mods-g...l#post11554605

750W of heat load on the RX480 is like 562W on the 360 Radiator (750*3/4)

So as you can see if you want a 10C delta (usually a good goal) you'll want around 1800 RPM fans. 1850 RPM GentleTyphoons would work nicely for this purpose. Your computer rarely manages to even get close to the TDP anyways, so you will usually be under 750W.