Great question, sigmasanti. I'm wondering the same thing: whether or not to go EVGA 670 FTW or MSI 670 PE in a R4.
It seems to me that the R4 would have plenty of airflow options, with two 140s in the front, a 140 in the bottom, and a 140 exhaust out the back. It looks as though the case has quite a bit of room to breathe inside, as long as the cables are nice and tidy. However, I'm pretty new to this.
Any thoughts or first-hand experience is very much appreciated.
I ended up asking around in some iirc channels and ended up buying a Gigabyte 670 (the model with three fans).
The Gigabyte 670 is inaudible, and has not reached temperatures above 68 c, even under extended gpu testing with furmark.
I am using the default setup in the R4 with one 140 in the front and one 140 in the back, keep them on the 7v (mid) setting.
In conclusion it probably does not matter which you go with, the R4 seems to have enough airflow to keep my single card cool. I would stick a fan in the bottom slot if you wanted to use SLI though. Since you are paying a premium for the R4 you probably want to keep the noise down, therefore I would recommend the MSI in this situation (the Gigabyte 670 OC though has been great though, I recommend it).
My system specs if they are useful:
Fractal Design R4
Intel i7 3770K
Coolermaster Hyper 212 EVO
8 gb G.Skill RAM
Gigabyte GTX 670 (GV-N670OC-2GD)
WD Caviar Black 1TB
My only notes on this build are that the Evo 212 is noisy (relative to the case fans and the gtx 670) and that the WD Caviar Black is noticeably loud during periods of high activity. I have not had any problems with temperatures due to the reduced airflow in the R4, and it is a beautiful case.