I have the same case, actually it's the white one, and well I paid extra for the Antec sticker on it not knowing they sold them under Chieftec. But anyway that's my case, and I installed that fan.

I also installed two others in front... But to step back a second, I currently have my setup as follows: One power supply fan, one case fan in back, and a CPU fan which are all three on at all times, all wired into the power supply.

I have a second group of fans however: Another rear case fan, three! in the front - two in the lower front of the case and that third in front of the hard drives. There's also a 486 heatsink and fan over the chipset for the motherboard. These are all wired together and all are also run off the power supply. The trick here is that I took all of the grounding wires and ran them together and then through a single on/off switch that I stuck in the front of the case.

When I'm surfing the internet or watching a DVD (I use my PC-DVD to watch movies on my television), I have the switch off and the small number of fans going. It's not as quiet as what most of you are describing, but it's never bothered me either. But if I'm gaming, or crunching DIVX movies or anything else intensive, I flip that switch on and launch the other four fans into motion. Yes it's loud, but it causes a mini tornado inside the case to keep it cool. And when I'm gaming the sound is turned up so loud I don't hear them.

Really my point is, if anyone's borderline on what is "adequate cooling", you might simply run a $1 switch to the ground wires so you could turn on or off your noise makers as needed.