I just built a new SFF rig. The case is a Lian-Li V354 and I'm running a i5 2500k cpu cooled by a Corsair H50 and I have two fans running it in a push pull config. Normally I prefer a Scythe S Flex fan like the F model for best airflow and noise but I tried a new fan. Noctua NF-P12 model. Twice the price of the Scythe model but its noise level is a few decibels lower. The two fans are powered by the mobo so they run at full speed. The other three case fans are run by a controller built into the case. I can tell you one thing is that these fans are very very quiet. Cannot even tell they are running unless you open up the case to look.
My two recommendations are the Scythe S Flex F model and the Noctua NF-P12. If you want to keep to a lower budget get the Scythe. If you have money to burn then get the Noctua.
Quick rundown of new build:
Lian-Li V354, 4xNoctua NF-P12-1300 Fans, Intel i5 2500k, ASUS P8P67-M Pro, 8GB GSkill RAM, HIS 6950, WD 1TB Black hdd, Corsair H50 CPU Cooler, Corsair HX850w PSU, Sony Optiarch AD-7710H-01, W7 Pro 64bit, I-INC 28" 1920x1200 LCD,Logitech G5, Saitek Eclipse II