A quiet build involves:
1. A quiet case - has no major openings other than those occupied by fans, and uses sound dampening materials on the side panels. I recommend Fractal Design Define R4.
2. Quiet case fans - downvolted with a fan controller to near-inaudible speeds. For a 140mm fan, that's around 400-500RPM. The included R4 fans are pretty good, but for optimal operation you'll want a second 140mm intake at the same RPM, all controlled by the integrated 3-speed controller at the lowest setting. The controller supports three fans.
3. Quiet internal components - the case dampening materials will help some, but you can't rely on the case to silence noisy components.
3a. CPU cooler with a low RPM or otherwise quiet fan. I recommend Scythe Mugen 3 and Thermalright HR-02 Macho for overclockers, though if you want truly quiet load noise levels, overclocking will be very limited. You could buy a nice heatsink like one of the above, and replace the fan with one that has similar constant RPM as your case fans
3b. PSU with at least Bronze efficiency and either a very low noise fan or passive operation (at least at idle). Passive operation probably unnecessary for a low wattage (<300W) PC
3c. Quiet video card cooler. Most nonreference coolers on current generation cards, like Asus DCII, MSI Twin Frozr, Gigabyte Windforce and such, are extremely quiet at stock clocks/volts and with a customized fan profile (using MSI Afterburner). For total silence, it's an option to buy an Arctic Cooling Accelero or Twin Turbo aftermarket heatsink, in which case I'd recommend an EVGA card because they'll honor warranty even if you remove the stock cooler.
3d. HDD's (optional) - 7200rpm drives make more noise, 5400RPM drives make less noise, SSD's make no noise. For a balance between cost, noise and capacity, buy one 128GB or 256GB SSD and a 1TB/2TB 5400RPM hard disk.
I'd recommend you create a thread over at General Hardware about your new build