Wanting to use watercooling not for the l33t uber-OC coolness but for the practicality of it seems a bit odd to me.
(That case is more holes than metal btw
You could use aircooling - A 25€ Big Shuriken, a €10 PWM-fan paired with a €2-cable used to connect the fan to your graphics card, and a custom fan profile in MSI Afterburner for your GTX 470 should bring the noise level down a whole lot, probably making the hardmounted HDD and PSU fan the loudest parts
Mount the fan between the perforated case panel and your GTX 470 (maybe you could remove the original fan & shroud) in the generous 45mm space (you only need 25mm! 45 mm is even enough to mount 2 Scythe Kaze Minis!