I am currently running my H100 in a HAF X as an exhaust with just the two stock fans pushing. I plan to keep the two stock fans, but I am trying to decide whether I should use a 200mm fan on top of the rad, or whether I should grab two more 120mm fans. I am looking more for performance than low-noise, but I don't want anything too ridiculously loud. It would be really awesome if I could find something with green LEDs too. Any suggestions?
edit: I'm thinking about two 120mm Coolermaster R4s, but I think I would have to hook them straight into the mobo because there are some compatibility issues with the h100. They seem like a decent option for the price (I can get 2 for $14) with ~70CFM, and they are rated for 19dba but I have read some reviews that say they are definitely louder than that at full speed (I have no fan controller other than the h100). Any other options I should be considering?
You'll get better performance using 4x120mm fans in push pull than the 200mm fan.
Those fans are pretty quiet - keep in mind 19 dBA is almost dead silent, so being able to hear them is technically louder than rated. Even 25 dBA isn't loud - you don't start getting problems until you get to about 30dBA.
I actually had them on my Hyper 212+ (green as well) and they moved a decent amount of air.
Cooler Master's fans are pretty good overall; using their cheapo 4-for-$10 ones on my PC, and I think they're rated for ~20 dBA and they're a little louder (probably ~25 dBA). However, they don't have the better/quieter sickle fan blade design.