I like liquid cooling systems, one of the reasons being that the radiator fan doubles as a chassis exhaust fan i.e. one fan doing the job of two.
I am currently using a Corsair CPU cooler with a 120 mm fan in push configuration. From what I have read this is as effective as pull, and there is always an option to mount an additional 120 mm fan in pull configuration to the outside of the case if you need it. Mounting a second radiator fan inside the case runs the risk of obscuring some of the RAM modules on the X79 Extreme4 board. A second radiator fan would push up noise levels, particularly with outside mounting.
With The X79 Extreme4, an i73930K CPU idling at Vcore 0.85V and x12 clock multiplier and a single exhaust fan, CPU temperatures run about 10-12C above ambient using a Cougar CF-V12HPB Vortex PWM Hydro-Dynamic-Bearing 120mm running at 1112 RPM. It is rated at 1500 RPM max, but under CPU load rotates at 1666 RPM. At 1112 RPM the fan is very quiet, and even at full tilt does not make too much noise.
Personally I favour 120 mm fans for a quiet PC option, but this may be a matter of taste so I'd recommend doing some research before committing.
Another consideration is the heat output of the X79 chipset. This runs pretty warm, so I use a 120 mm chassis fan running at about 780 RPM to move air over the southbridge. It stabilises at about 20C above ambient. The X79 Extreme4 comes with a small cooling fan mounted on the southbridge which at default setting starts up at a bit over 50C. I try to avoid its use as it is a little noisy.
If you have a full tower case already you may be able to fit a 120 mm radiator cooler system and 120 mm chassis fans OK, but you may be better off purchasing a new case with a bottom mounted PSU. This gives more room for CPU cooling options at the top of the case.