I use two (intake & exhaust) GT 1450's in a Lian Li PC-A05NB and have a Xigmatek HDT-S1283 heatsink with a Scythe 120mm PWM fan (DFS122512L-PWM) and honestly you have to stick your head by the box to hear it. Running an older system that will be upgraded this winter, but it has E8400, Gigabyte GA-P35-DS3L, G.Skill 4GB, GTX 460, X25-M, WD Black 640, Seagate 7200.10, Corsair 620HX, Win 7. Granted, I have 6 kids so very rarely is it dead silent in our house, but even after everyone has gone to sleep the machine is very quiet.
For comparison, my other machine is housed in an Antec Solo. Specs are: i5 750, Gigabyte GA-P55M-UD2, G.Skill 4GB, GTX 460, ViXS Puretv-u 48b0, X25-M, WD Black 640, WD Green 1TB, Seagate 7200.10, Seasonic X650, Win 7. Front fan is a 100mm Scythe FDB, Rear is a Scythe S-Flex SFF21E. Only problem is I have the stock Intel Cooler running on the i5 which I will be replacing this weekend with a Cooler Master Hyper 212+ and a Scythe 120mm PWM fan (found a new Scythe FDB PWM fan SA1225FDB12H-P to try out). Probably going to try out a Scythe 140mmm for exhaust(that is made for 120mm fan opening) and a 92mm Scythe FDB PWM fan for the front intake. I can hear a fan, which I believe is the Intel Cooler which drives me nuts but no one else notices. This is the "family" machine so whenever I mess with it I can't have it down for long. I don't believe that the Scythe fans are loud, but I need to replace the Intel Cooler to see how the noise changes and see if that is the primary source of noise, then I'll work on the other fans if so.
I really have been impressed with the GT fans in the Lian Li case. They move a decent amount of air and temp's are great. At idle, CPU is right around 41º and GPU is 39º. The GTX 460 helps in the Lian Li as it is a shorter card and cooler running with the fan running most times at about 30%. There are some hotspots in the case, but I have not had an issue so far.