check out the reviews at
www.overclockers.com in their watercooling section
i find that that is the best place to go for watercooling kits comparison
piping is cheap
the expensive parts are the radiator, block, pump...
best is to make your own reservoir, get a Hydor L30 pump, get a radiator or heatercore for cheap from autoparts store or hardware stores or even junkyards
some people make their own blocks but ud have to be very good with machine works
i think dangerden makes some decent ones but not as good as the polarflo which you might be able to get some discount from if you mention techwarelabs