5 bucks, eh?
The res is not a substitute for a rad. The water temp would slowly climb, and climb, and climb... until the pool of water can dissipate as much heat into the air, as the CPU is putting in the water. Can you see the vapor?
Unfortunately, there are still fans, in most watercooled rigs. If you're on a budget, I'm not going to suggest the watercooled PSU mod...
I will however suggest modding the fans inside the PSU, with the 7 volt mod, or even simpler (and perhaps safer), add a rheostat to lower those fan speeds.
As for the radiator, I'm still toying with the idea of using a sqirrel cage blower, instead of axial fans (commonly found types). It should provide a very high flow, with very little noise.
In your case, shrouding should do you. Add some rubber mounts here and there, and you should be happy.
In any case, controlling the fan speed is probably going to be the single best service that you can do yourself.
Need a link?
BTW, the tall pipe cooling thing is a bong. Unless you don't mind the continous shower sound, it'll work OK.