Oops, sorry thought you said RX not EX. In my testing at 1800rpm the RS and EX were about the same. An RX upgrade would be worth about a 10% improvemt ( 1 degree if your water air delta is 10c), but no improvemnt from RS to EX. EX is just a more slow speed fan tuned from what I got. Some other testing shows different results, but I retested a couple of time and continued to get a similar result.
i did find there is also some gain using shrouds on the RS series rads, but that too would take space.
Switching to something like the Swiftech MCR XP series would gain a little with the high speed fans, but really no rad change is going to make a big difference. If anything, switching the fans out to GT AP-29s for more RPM would probably do the most good if you don't mind the noise.
Typical that most rad differences can be made up with 50-100 rpm in fan speed, so adding 500rpm is a much bigger improvement than rad change.Edited by Martinm210 - 1/25/13 at 8:01am