bigger ID the better. more flow, less asthma. What's the max it can take?? I wouldnt bother exceeding the ID of the inlet holes on the waterblocks.
The difference in tubing size has been prove to be less than 1C difference.http://www.ocforums.com/showthread.php?t=515368
I couldnt imagine more than 300 watts. 400 would be insane estimation.
600w seems low for a 360 rad with high speed fans.
water cools really well. the hotter the components, the more it does. as the room temp difference is greater, the water cooling radiators transfer heat faster.
Water absorbs heat at the speed the CPU water block can transfer it. All blocks are different in this speed. If the ambient temp was to change it would affect both air or water cooling the same.
WC is not to keep components cooled to very low temps, its for keeping gaming machines and power machines always temperate at very quiet levels. 24/7 WC setups take a day to even out to stable temps from what I have seen.
Water keeps you components cooler, most of the time the thing limiting our CPU OC is heat. Water gives us lower temps and sometime if its in the chip a few more Mhz. Water in a small closed loop would take 1-2 hours at most to even out.
El Jefe stop spreading your crap.