I've just recently moved, and most of my gear is in storage untill we get a larger place, so I cant post any hard data on flowrates for my 9x9x2 heatercore.
The design of the heatercore will be the big kicker for you, I think. You might also give some thought to going with larger fans than the 120mm models you're thinking of since the rad will be so large. Let me know what you find. I'd be interested in one that size myself.
I'm assuming you're putting it in a seperate enclosure, given its size. You might have a problem with head loss, depending on the distances involved. Just something to think about.
Pictures of my gear can be found
here