Not exactly - I was saying
"break the problem down". Yes, you have to guess - but you can guess in
two parts. I would guess, for instance, 250 sq cm at a minimum, for cooling about 120W and keeping coolant two to four C over the temp of the air you're pulling through. I'm not worrying about pump, tubing, water flow, water pressure, or water blocks, for
this guess. Yep, still a guess, though.
The second guess is easier (pump, tubing, wbs) thanks to all the work Phaestus, BillA, Les, et al have done for us.
If by dual heatercore you mean BI (pro or xtreme) II, or a heatercore that'll take 2 120mm fans, then, yeah, that ought'a work fine. The thinner rads have the advantage of needing less air pressure (so quieter fans). If you don't care about fan noise, don't optimize for this, of course... And if you
do care about fan noise, then adding more powerful fans is the last thing you'd want to do
