My choice for PWM fans are Scythe Slip Stream 120mm x 25mm PWM Mid Speed Fan - (SY1225SL12LM-P)
, cheap and they have a very good range (300-1300rpm), as long as your bios/software can control them imo are good choice.
Now if have a bigger budget or want something a little better, i would probably go with Noiseblocker NB-eLoop B12-PS 120mmx25mm Ultra Silent Bionic Blade PWM Fan - 400 - 1500 RPM
or Noctua NF-F12 120 x 25mm PWM Fan
. Personally i would go with the scythe, its less than half price of these fans.
For connecting the two pwm fans i would use Y PWM splitter, something like Akasa PWM Splitter Cable (AK-CBFA04-15)
. Now if you are worried about the mobo connector now having enough power for 2 fans, you can get a splitter that uses a direct 4pin molex for power, and just uses the mobo for reporting the rpm and grabbing the pwm signal, Akasa PWM Splitter - Smart Fan Cable (AK-CB002)
But i wouldnt expect to much from a gigabyte mobo and their fan control, not their biggest strenght, if you want more control and tweaking go with Asus and their FanXpert2.