Hi,
I can recommend buying NH-U14S.
You can search for reviews and take a look, that this model is very close to D15.
But it's cheaper, less heavy and a lot more compatible with high ram sticks.
It has a 140mm pwm fan, second can be attached. At it's lowest 250 rpm the fan is very quiet.
You can set the fan into the "pull" position to have 100% compatibility with any ram.
I use one myself. I have IX Formula and low-profile corsair XLP ram.
But this cooler allows me to install something like corsair dominator ram with very high heatsinks.
I wanted a different ram, but didn't want to take a risk.
Was thinking about AIO too, but it's much more loud, unreliable (in comparisone with air) and does not offer THAT MUCH a performance advantage.
In tests AIO's usually have around 5c advantage in temp and 30 dB "advantage" in sound.... for double the price, a chance of pump failure and leakage.
P.S If I were you, I would sit with a standart box cooler and save some money.
I'm sure, you will survive a few months without OC'ing your CPU.