Take a paper tube and use it as a stethoscope to identify the source of your noise.
It comes from fans running at high rpm's.
My guess is the graphics cards are the primary source.
What are some options?
First of all, a liquid cooler will not reduce noise.
They typically include two high rpm fans for the radiator which will be louder than what you have.
The best quiet coolers will have 1 or 2 140mm fans which can push more air at lower rpm.
Look at Phanteks or noctua for two of the best.
If your psu is running at max, the fan will make some noise. A new gold rated psu that is overprovisioned by 20% will be quieter.
One of the best quiet cases will be the Fractal design define R4.
It is the case used in the spcr( www.silentpcreview.com ) quiet gaming build
http://www.silentpcreview.com/article1420-page1.html
GTX770 are fine cards, but are not as strong or as quiet as GTX970 or GTX980 cards.
I doubt that you would want to change them out, but you could experiment with reducing any overclocks and the associated fan speed profiles.