I run my d5 vario at 5, which is the highest speed. I can't hear it when sitting at my desk with it on tune floor. A fan at 1100rpm is slightly audible and louder than the pump. My girlfriends vario set to 4 I can barely hear because her room is more silent.
Under 1000rpm the performance between thick and slim radiators is similar. Lower rpm you want lower fin density to let air pass through easier. The faster air speed will cool better. At low rpm, thicker radiators of equal fin density often slow down the air to the point that there is negative impact on cooling, which is why thinner radiators often work equal if not better for silent builds, so long as they are low fpi.
There is very good radiator data here http://www.xtremerigs.net/2015/02/11/radiator-round-2015/
Its a 360mm roundup, but you can scale it up and down a bit... A 480 is a little less than 4/3 of a 360, since the wattage dissipated on the tank ends is the same on 120-480... without doing complicated math, you can get into the ballpark by 2/3 for a 240 and 4/3 for a 480...
I'm not too familiar with the radiator capacity of the cases... but if you can fit 2x480, and 1x360... your good for the dual loop. My general outlook, is better to have more radiator than needed, than to need more radiator and not have it.Edited by EMUracing - 4/25/17 at 1:25am