Radiator directly onto case. Shroud on inside of rad. Fans on Shroud. Fans sucking air in thru case, thru rad, thru shroud, venting into case. Balance incoming air with more fans pulling out than pull in. ie: 3x120's pulling in, 4x 120's pushing out, or 3x 120s and 1x 80. The outlet fans provide more umph than the fans on the rad, so will cause additional air to be pulled thru than 3x rad fans sucking on their own.
Always better to have more fans pulling air out than fans pulling air in. Keeps internal pressure low as well.
That offers lowest noise vs best performance combination.
The new ThermoChills aren't dual PA160s... they're simply the HE Series reworked to be more efficient with less noise. As they stand the HE Series requires fans with hefty pressure to penetrate it's dense core. Now that watercooling attitudes have changed over the past few years, they're getting reworked based on results of PA160 testing to achieve the same low noise, gr8 performance (again, should actually be better than HE series as it stands currently but time will tell), with weak ass <20dBa fans.
Cathar currently has the prototypes of these reworks and again they are confirming and beating the theoretical models on which the changes were based. The models were drawn up from results of PA160 with various fans and flowrates. Take the answer to an equation, and you can always work it backwards and change the formulae so to speak. We can produce the same outcome by tweaking design parameters of the current HE series, meaning easy installation as back to 120mm footprint.
These reworked rads will be released as the PA120.x line...
Results of testing won't be released for another month or two... Cathar is awaiting a second bundle from myself including original HE series and shrouds for direct comparison etc.