Throw a thread up in Overclocking section, there a W/c hideout over there http://www.tomshardware.co.uk/forum/forum-11.html
I'll answer some of your queries here though,
No idea of exact numbers depends if your clocking or not, decent enough ones though
if you go real water, no coloured/premix fluids, distilled water and silver killcoils are sufficient (unless you are up for cleaning out your loop every few months?
you can just buy uv blue tubing instead and relax
The RX series is better, thicker rads cool better
and once you post over that side, we'll draw you up a loop plan
what components are you intending on cooling?
overclocking? if so, how much?
See you on the wetside