LED fans must still be pretty popular. The 3 140mm ones came with the Carbide Air. Two already had LEDs I just changed the LEDs out for the crazy disco ones. The LEDs were glued in so I had to dremel them out and I'm really concerned about the fumes that it made...
All the others were free after rebate which I did get without fail. The motherboard has more 3pin connectors than 4pin and the BIOS supports 4 different speeds so the sound is very nice on the lower settings.
PWM fans can sound louder at lower speeds then standard because of harmonics. Is not always the case but sometimes it happens.
As far as performance the two r9 290x GPUs can (and have) run full tilt 24/7 and the GPUs stay under 65c with no increase in noise level 
well slight increase, I have two stock Intel CPU fans on my GPU VRM heatsinks which are set to kick on 75% when GPUs hit 60c.
If you know anything about r9 290s their typical behavior is to hit 95c within 10 minutes and start throttling down to a lower speed. Not to mention the noise levels.
so you can see its not all show and no go:
http://www.3dmark.com/fs/3216378
In Sweden I mostly see young people using LED fans, most enthusiast do not like em since most of them not are not performance fans and CFM vs Noise levels are not at the best ratio. But as I said people can use whatever they like and fits their need, as long as they move enough air for your needs and you don't mind their dB levels there is nothing wrong with them
PWM fans are no problem when using the right brands that's why I use Noctua and Cougar, Noctua is one of the best fans on the market and have been for quite some time, their air CPU coolers are also the best air coolers, now I use water cooling in my Workstation/gaming rigs and the Cougar fans I'm using actually are designed to push air trough Radiators, quite the difference in fans depending what they are made for and how they push the air and that also makes a impact on how they sound, some fans sound horrible when pushing air into the case but sounds as they should when paired up on radiators etc.
I see you are using pre-built water coolers with the pump built in the block, on them you will be fine with pretty much most fans, they are quite slim so not as important what fan you use there
Looks like you are using PnP configuration on tha rads also?
I know very well how the 290x heat monsters work since I also have two of them and with the stock ref cooling they where obnoxious but when they are on water they are really nice cards
Also I am a heavy overclocker which probably is the reason I have spend quite the time over the years dwelling into the fan jungle
Now we gotta keep on topic again, went way overboard haha
