Honestly, any 120mm fan that spins at 1500rpm is gonna be fairly audible. They'll probably be better than thoes Vantec UVs, but I doubt they'll be anywhere near silent considering the 1200rpm CM UV is not completely silent either. Additionally, that Aerocool looks like it's geared more towards bling anyway.

I recommend you try getting some Yate Loons/Scythes/CM UVs, undervolting them to run at about 1000rpm or so and see how it goes. IF your temps don't suffer too much, you'll probably have a pretty quiet fan setup. Which will of course make you notice other things like HDD seek noise and PWM whine.

It depends on your PSU. Some are fixed speed.
But most new PSUs today have variable speed fans that are thermally controlled. So if the temperature rises, so will the speed of the PSU fan and consequently, noise levels will increase.

As for those 2 locations, I doubt there'll be much difference.