You can buy a fan speed controller which you slot into either a 3 1/2" or 5 1/4" drive bay on the front of your PC, looks cool, only requires 1 molex power connector to power all of your fans, and you can set them to be quiet or full speed or whatever. Im using a Scythe Master ACE.
You CAN connect the fans directly to your PSU but then they will be full speed all of the time and possibly quite noisy.
That is if the Antec 900 doesn't come with a built in controller, I'm not sure.....
hunter315 has spotted the real situation. The description of the Antec 900 I read says it comes with 4 fans altogether: 1 200 mm fan mounted in the top of the case, one 120 mm TriCool mounted in the back, and two 120 mm TriCools with blue LEDS that are intended to mount in the front as intake fans blowing air over the HDD's.
The 200 mm top fan can be plugged into the mobo's SYS_FAN1 port so the mobo can power it (and maybe control its speed?). The CPU cooler plugs into the CPU_FAN port on the mobo. But the three TriCool fans all can not plug into a common 3-pin mobo pinout anyway. They come equipped with a 4-pin Molex connector that plugs directly into an output connector from the PSU. (By the way, if you need more of those, any computer shop can sell you a splitter that makes 2 Molex outputs from 1.) This gives each TriCool a full 12 VDC supply. Then each also comes with its own little 3-position switch already connected on the end of a short wire. You use these to set the fan's speed manually to Low, Med or Hi. There is no mobo-based automatic control system for TriCool fans.